Add user follows to following feed

app/feature_schema.py

@@ -1,4 +1,4 @@
-"""Startup equivalents of migrations 19–22 (kept in sync by tests)."""
+"""Startup equivalents of migrations 19–23 (kept in sync by tests)."""
 
 FEATURE_SCHEMA = (
     '''CREATE TABLE IF NOT EXISTS push_devices (
@@ -55,4 +55,13 @@ FEATURE_SCHEMA = (
         ON push_notifications(available_at) WHERE state='pending';''',
     '''CREATE UNIQUE INDEX IF NOT EXISTS idx_user_badges_registration_cohort
         ON user_badges(user_id) WHERE badge_code IN ('alpha_tester', 'beta_tester', 'early_bird');''',
+    '''CREATE TABLE IF NOT EXISTS followed_users (
+        follower_id INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+        followed_id INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+        created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
+        PRIMARY KEY (follower_id, followed_id),
+        CHECK (follower_id <> followed_id)
+    );
+    CREATE INDEX IF NOT EXISTS idx_followed_users_followed
+        ON followed_users(followed_id, follower_id);''',
 )