feat: custom claims (#53)

backend/migrations/20241028064959_custom_claims.down.sql

@@ -0,0 +1 @@
+DROP TABLE custom_claims;

backend/migrations/20241028064959_custom_claims.up.sql

@@ -0,0 +1,15 @@
+CREATE TABLE custom_claims
+(
+    id            TEXT NOT NULL PRIMARY KEY,
+    created_at    DATETIME,
+    key           TEXT NOT NULL,
+    value         TEXT NOT NULL,
+
+    user_id       TEXT,
+    user_group_id TEXT,
+    FOREIGN KEY (user_id) REFERENCES users (id) ON DELETE CASCADE,
+    FOREIGN KEY (user_group_id) REFERENCES user_groups (id) ON DELETE CASCADE,
+
+    CONSTRAINT custom_claims_unique UNIQUE (key, user_id, user_group_id),
+    CHECK (user_id IS NOT NULL OR user_group_id IS NOT NULL)
+);