Add forgotten file

Author: gefjon

docs/docs/00200-core-concepts/00200-functions/00600-HTTP-handlers.md

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+---
+title: HTTP Handlers
+slug: /functions/http-handlers
+---
+
+import Tabs from '@theme/Tabs'
+import TabItem from '@theme/TabItem'
+
+HTTP handlers allow a SpacetimeDB database to expose an HTTP API.
+External clients can make HTTP requests to routes nested under [`/v1/database/:name_or_address/route`](../../00300-resources/00200-reference/00200-http-api/00300-database.md#any-v1databasename_or_identityroutepath); these requests are resolved to routes defined by the database and then passed to the corresponding HTTP handler.
+
+:::warning
+***HTTP handlers are currently in beta, and their API may change in upcoming SpacetimeDB releases.***
+:::
+
+## Defining HTTP Handlers
+
+<Tabs groupId="server-language" queryString>
+<TabItem value="rust" label="Rust">
+
+Because HTTP handlers are unstable, Rust modules that define them must opt in to the `unstable` feature in their `Cargo.toml`:
+
+```toml
+[dependencies]
+spacetimedb = { version = "2.*", features = ["unstable"] }
+```
+
+Define an HTTP handler by annotating a function with `#[spacetimedb::http::handler]`.
+
+The function must accept exactly two arguments:
+
+1. A  `&mut spacetimedb::http::HandlerContext`.
+2. A `spacetimedb::http::Request`.
+
+The function must return a `spacetimedb::http::Response`.
+
+```rust
+use spacetimedb::http::{Body, handler, HandlerContext, Request, Response};
+
+#[handler]
+fn say_hello(_ctx: &mut HandlerContext, _req: Request) -> Response {
+    Response::new(Body::from_bytes("Hello!"))
+}
+```
+
+</TabItem>
+</Tabs>
+
+## Registering Handlers to Routes
+
+Once you've [defined an HTTP handler](#defining-http-handlers), you must register it to a route in order to make it reachable for requests.
+
+<Tabs groupId="server-language" queryString>
+<TabItem value="rust" label="Rust">
+
+All routes exposed by your module are declared in a `spacetimedb::http::Router`. Register the `Router` for your database by returning it from a function annotated with `#[spacetimedb::http::router]`.
+
+```rust
+use spacetimedb::http::{router, Router};
+
+#[router]
+fn router() -> Router {
+    Router::new()
+        .get("/say-hello", say_hello)
+}
+```
+
+Add routes within a router with the `get`, `head`, `options`, `put`, `delete`, `post`, `patch` and `any` methods, which register an HTTP handler for that HTTP method at a given path.
+
+Nest routers with `router.nest(prefix, sub_router)`, which causes `sub_router` to handle routing for all paths that start with `prefix`.
+
+Combine routers with `router.merge(other_router)`, which combines both routers.
+
+</TabItem>
+</Tabs>
+
+### Strict Routing
+
+SpacetimeDB uses strict routing, meaning that a request must match a path exactly in order to be routed to that handler. Trailing slashes are significant.
+
+## Sending Requests
+
+Routes defined by a SpacetimeDB database are exposed under the prefix `/v1/database/:name/route`. To access the `say-hello` route above, send a request to `$SPACETIMEDB_URI/v1/database/$DATABASE/route/say-hello`, where `$SPACETIMEDB_URI` is the SpacetimeDB host (usually `https://maincloud.spacetimedb.com`), and `$DATABASE` is the name of the database.