feat: add DB table to store GTFS feed availability checks (#1703)

Author: davidgamez

liquibase/changelog.xml

@@ -109,6 +109,8 @@
     <include file="changes/feat_task_execution_log.sql" relativeToChangelogFile="true"/>
     <!-- Add MD5 hash column to GTFSDataset table. -->
     <include file="changes/feat_1657.sql" relativeToChangelogFile="true"/>
+    <!-- Add table to store GTFS feed availability check results. -->
+    <include file="changes/feat_1700.sql" relativeToChangelogFile="true"/>
     <!-- Keep this at the very end to ensure all table and schema changes
          are applied before materialized views are (re)created. -->
     <include file="materialized_views/materialized_views.xml" relativeToChangelogFile="true"/>

liquibase/changes/feat_1700.sql

@@ -0,0 +1,39 @@
+-- Add table to store GTFS feed availability check results (issue #1700).
+-- Supports feed availability analysis as described in epic #1699.
+CREATE TYPE availability_check_request_type AS ENUM (
+    'http_head',
+    'http_get'
+);
+
+CREATE TABLE IF NOT EXISTS gtfs_feed_availability_check (
+    id           UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+
+    feed_id      VARCHAR(255) NOT NULL,
+    checked_at   TIMESTAMPTZ NOT NULL DEFAULT now(),
+
+    request_url  TEXT NOT NULL,
+    request_type availability_check_request_type NOT NULL,
+    status_code  INTEGER,
+    latency_ms   INTEGER,
+
+    error_message TEXT,
+    error_type   VARCHAR(255),
+
+    success      BOOLEAN NOT NULL,
+
+    created_at   TIMESTAMPTZ NOT NULL DEFAULT now(),
+
+    CONSTRAINT gtfs_feed_availability_check_feed_id_fkey
+        FOREIGN KEY (feed_id)
+        REFERENCES gtfsfeed(id)
+        ON DELETE CASCADE
+);
+
+CREATE INDEX IF NOT EXISTS idx_gtfs_feed_availability_check_feed_checked_at
+    ON gtfs_feed_availability_check (feed_id, checked_at DESC);
+
+CREATE INDEX IF NOT EXISTS idx_gtfs_feed_availability_check_checked_at
+    ON gtfs_feed_availability_check (checked_at DESC);
+
+CREATE INDEX IF NOT EXISTS idx_gtfs_feed_availability_check_feed_success_checked_at
+    ON gtfs_feed_availability_check (feed_id, success, checked_at DESC);