docs: in_systemd: fix defaults, grammar, whitespace (#2358)

- Change boolean defaults from 'off' to 'false' to match source
  code: lowercase, read_from_tail, strip_underscores
  - Fix grammar in db.sync description: add comma and 'see the'
  before link
  - Remove trailing whitespace after backslash in command-line
  example

Fixes #2357

Signed-off-by: Eric D. Schabell <eric@schabell.org>

Author: eschabell

pipeline/inputs/systemd.md

@@ -9,13 +9,13 @@ The plugin supports the following configuration parameters:
 | Key                   | Description                                                                                                                                                                                                                                                                                                                                                   | Default |
 |:----------------------|:--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|:--------|
 | `db`                  | Specify the absolute path of a database file to keep track of the `journald` cursor.                                                                                                                                                                                                                                                                          | _none_  |
-| `db.sync`             | Set a default synchronization (I/O) method. Possible values: `extra`, `full`, `normal`, and `off`. This flag affects how the internal SQLite engine synchronizes to disk. For more details [SQLite documentation](https://www.sqlite.org/pragma.html#pragma_synchronous). Available in Fluent Bit v1.4.6 and later.                                                    | `full`  |
-| `lowercase`           | Lowercase the `journald` field (key).                                                                                                                                                                                                                                                                                                                         | `off`   |
+| `db.sync`             | Set a default synchronization (I/O) method. Possible values: `extra`, `full`, `normal`, and `off`. This flag affects how the internal SQLite engine synchronizes to disk. For more details, see the [SQLite documentation](https://www.sqlite.org/pragma.html#pragma_synchronous). Available in Fluent Bit v1.4.6 and later.                                          | `full`  |
+| `lowercase`           | Lowercase the `journald` field (key).                                                                                                                                                                                                                                                                                                                         | `false` |
 | `max_entries`         | When Fluent Bit starts, the Journal might have a high number of logs in the queue. To avoid delays and reduce memory usage, use this option to specify the maximum number of log entries that can be processed per round. Once the limit is reached, Fluent Bit will continue processing the remaining log entries once `journald` performs the notification. | `5000`  |
 | `max_fields`          | Set a maximum number of fields (keys) allowed per record.                                                                                                                                                                                                                                                                                                     | `8000`  |
 | `path`                | Optional path to the Systemd journal directory. If not set, the plugin uses default paths to read local-only logs.                                                                                                                                                                                                                                            | _none_  |
-| `read_from_tail`      | Start reading new entries. Skip entries already stored in `journald`.                                                                                                                                                                                                                                                                                         | `off`   |
-| `strip_underscores`   | Remove the leading underscore of the `journald` field (key). For example, the `journald` field `_PID` becomes the key `PID`.                                                                                                                                                                                                                                  | `off`   |
+| `read_from_tail`      | Start reading new entries. Skip entries already stored in `journald`.                                                                                                                                                                                                                                                                                         | `false` |
+| `strip_underscores`   | Remove the leading underscore of the `journald` field (key). For example, the `journald` field `_PID` becomes the key `PID`.                                                                                                                                                                                                                                  | `false` |
 | `systemd_filter`      | Perform a query over logs that contain specific `journald` key/value pairs. For example, `_SYSTEMD_UNIT=UNIT`. The `systemd_filter` option can be specified multiple times in the input section to apply multiple filters.                                                                                                                                    | _none_  |
 | `systemd_filter_type` | Define the filter type when `systemd_filter` is specified multiple times. Allowed values: `and`, `or`. With `and` a record is matched only when all `systemd_filter` have a match. With `or` a record is matched when any `systemd_filter` has a match.                                                                                                | `or`    |
 | `tag`                 | Fluent Bit uses tags to route messages. For the Systemd input plugin, tags have an additional capability: if the tag includes a wildcard (`*`), it will be expanded with the Systemd Unit file (`_SYSTEMD_UNIT`, like `host.* => host.UNIT_NAME`) or `unknown` (`host.unknown`) if `_SYSTEMD_UNIT` is missing.                                                              | _none_  |
@@ -32,7 +32,7 @@ From the command line you can let Fluent Bit listen for Systemd messages with th
 ```shell
 fluent-bit -i systemd \
            -p systemd_filter=_SYSTEMD_UNIT=docker.service \
-           -p tag='host.*' \ 
+           -p tag='host.*' \
            -o stdout
 ```