fix: export from SQLite fails to import into Postgres because of mismatched schemas

backend/resources/migrations/postgres/20261006120000_sqlite_postgres_schema_alignment.down.sql

@@ -0,0 +1,7 @@
+ALTER TABLE audit_logs ALTER COLUMN created_at DROP NOT NULL;
+ALTER TABLE audit_logs ALTER COLUMN user_agent DROP NOT NULL;
+ALTER TABLE kv ALTER COLUMN value DROP NOT NULL;
+ALTER TABLE oidc_clients ALTER COLUMN created_at DROP NOT NULL;
+ALTER TABLE users ALTER COLUMN first_name DROP NOT NULL;
+ALTER TABLE users ALTER COLUMN last_name DROP NOT NULL;
+ALTER TABLE webauthn_credentials ALTER COLUMN created_at DROP NOT NULL;

backend/resources/migrations/postgres/20261006120000_sqlite_postgres_schema_alignment.up.sql

@@ -0,0 +1,24 @@
+-- Declare the columns that are NOT NULL on SQLite as NOT NULL too, so an export from either database can be imported into the other
+-- The application never writes NULL into these columns, but backfill any NULL left over from older versions first
+-- Empty strings are what the application writes for these values and what readers of kv treat as missing
+
+UPDATE audit_logs SET created_at = now() WHERE created_at IS NULL;
+ALTER TABLE audit_logs ALTER COLUMN created_at SET NOT NULL;
+
+UPDATE audit_logs SET user_agent = '' WHERE user_agent IS NULL;
+ALTER TABLE audit_logs ALTER COLUMN user_agent SET NOT NULL;
+
+UPDATE kv SET value = '' WHERE value IS NULL;
+ALTER TABLE kv ALTER COLUMN value SET NOT NULL;
+
+UPDATE oidc_clients SET created_at = now() WHERE created_at IS NULL;
+ALTER TABLE oidc_clients ALTER COLUMN created_at SET NOT NULL;
+
+UPDATE users SET first_name = '' WHERE first_name IS NULL;
+ALTER TABLE users ALTER COLUMN first_name SET NOT NULL;
+
+UPDATE users SET last_name = '' WHERE last_name IS NULL;
+ALTER TABLE users ALTER COLUMN last_name SET NOT NULL;
+
+UPDATE webauthn_credentials SET created_at = now() WHERE created_at IS NULL;
+ALTER TABLE webauthn_credentials ALTER COLUMN created_at SET NOT NULL;