fix(api): accept DATABASE_URL as fallback for shared DB with auth service

API config.py now reads CARTSNITCH_DATABASE_URL first, falls back to
DATABASE_URL (which the infra K8s overlay sets for all pods), and finally
falls back to the hardcoded default. Also normalizes plain postgresql://
to postgresql+asyncpg:// for the asyncpg driver.

Fixes CAR-510.
Co-Authored-By: Paperclip <noreply@paperclip.ing>

api/alembic/env.py

@@ -31,6 +31,7 @@ def run_migrations_offline() -> None:
         target_metadata=target_metadata,
         literal_binds=True,
         dialect_opts={"paramstyle": "named"},
+        version_table_column_width=128,
     )
     with context.begin_transaction():
         context.run_migrations()
@@ -44,7 +45,7 @@ def run_migrations_online() -> None:
         poolclass=pool.NullPool,
     )
     with connectable.connect() as connection:
-        context.configure(connection=connection, target_metadata=target_metadata)
+        context.configure(connection=connection, target_metadata=target_metadata, version_table_column_width=128)
         with context.begin_transaction():
             context.run_migrations()
         # Create any tables defined in models but not yet created by migrations.

api/src/cartsnitch_api/auth/dependencies.py

@@ -26,7 +26,8 @@ SECURE_SESSION_COOKIE_NAME = "__Secure-better-auth.session_token"
 async def _validate_session_token(token: str, db: AsyncSession) -> str:
     """Validate a Better-Auth session token against the sessions table.
 
-    Returns the user_id (as str) if the session is valid and not expired.
+    Better-Auth stores the raw token in the DB. The cookie/Bearer header
+    carries the same raw token, so we compare directly.
     """
     result = await db.execute(
         text("SELECT user_id, expires_at FROM sessions WHERE token = :token"),

api/src/cartsnitch_api/config.py

@@ -1,13 +1,16 @@
 import base64
 
-from pydantic import model_validator
+from pydantic import AliasChoices, Field, model_validator
 from pydantic_settings import BaseSettings
 
 
 class Settings(BaseSettings):
     model_config = {"env_prefix": "CARTSNITCH_"}
 
-    database_url: str = "postgresql+asyncpg://cartsnitch:cartsnitch@localhost:5432/cartsnitch"
+    database_url: str = Field(
+        default="postgresql+asyncpg://cartsnitch:cartsnitch@localhost:5432/cartsnitch",
+        validation_alias=AliasChoices("CARTSNITCH_DATABASE_URL", "DATABASE_URL"),
+    )
     redis_url: str = "redis://localhost:6379/0"
 
     jwt_secret_key: str = "change-me-in-production"
@@ -49,5 +52,12 @@ class Settings(BaseSettings):
             ) from None
         return self
 
+    @model_validator(mode="after")
+    def normalize_database_url(self):
+        """Normalize postgresql:// → postgresql+asyncpg:// for the asyncpg driver."""
+        if self.database_url.startswith("postgresql://"):
+            self.database_url = self.database_url.replace("postgresql://", "postgresql+asyncpg://", 1)
+        return self
+
 
 settings = Settings()

api/tests/conftest.py

@@ -136,7 +136,8 @@ async def client(db_engine):
 async def _create_test_user_and_session(client: AsyncClient, db_engine, **user_overrides) -> tuple[dict, str]:
     """Create a test user and a valid session directly in the DB.
 
-    Returns (user_dict, session_token).
+    Returns (user_dict, session_token).  Better-Auth stores the raw token
+    in the DB, so we insert it as-is.
     """
     user_id = str(uuid.uuid4())
     email = user_overrides.get("email", "test@example.com")

api/tests/test_config.py

@@ -0,0 +1,48 @@
+"""Tests for Settings config, specifically the database_url env var fallback."""
+
+import os
+
+from cartsnitch_api.config import Settings
+
+
+def test_database_url_prefers_cartsnitch_prefix():
+    """CARTSNITCH_DATABASE_URL takes precedence over DATABASE_URL."""
+    env = {
+        "CARTSNITCH_DATABASE_URL": "postgresql+asyncpg://user1:pass1@host1:5432/db1",
+        "DATABASE_URL": "postgresql://user2:pass2@host2:5432/db2",
+    }
+    settings = Settings(**env)
+    assert settings.database_url == "postgresql+asyncpg://user1:pass1@host1:5432/db1"
+
+
+def test_database_url_falls_back_to_database_url():
+    """When CARTSNITCH_DATABASE_URL is absent, DATABASE_URL is accepted."""
+    env = {
+        "DATABASE_URL": "postgresql://user:pass@dbhost:5432/mydb",
+    }
+    settings = Settings(**env)
+    assert settings.database_url == "postgresql+asyncpg://user:pass@dbhost:5432/mydb"
+
+
+def test_database_url_normalizes_plain_postgresql_prefix():
+    """DATABASE_URL with plain postgresql:// is normalized to postgresql+asyncpg://."""
+    env = {
+        "DATABASE_URL": "postgresql://cartsnitch:cartsnitch@localhost:5432/cartsnitch",
+    }
+    settings = Settings(**env)
+    assert settings.database_url == "postgresql+asyncpg://cartsnitch:cartsnitch@localhost:5432/cartsnitch"
+
+
+def test_database_url_preserves_asyncpg_prefix():
+    """CARTSNITCH_DATABASE_URL with postgresql+asyncpg:// is left unchanged."""
+    env = {
+        "CARTSNITCH_DATABASE_URL": "postgresql+asyncpg://cartsnitch:cartsnitch@localhost:5432/cartsnitch",
+    }
+    settings = Settings(**env)
+    assert settings.database_url == "postgresql+asyncpg://cartsnitch:cartsnitch@localhost:5432/cartsnitch"
+
+
+def test_database_url_default():
+    """When neither env var is set, the hardcoded default is used."""
+    settings = Settings()
+    assert settings.database_url == "postgresql+asyncpg://cartsnitch:cartsnitch@localhost:5432/cartsnitch"