feat: implement get session by user

db/sqlc/queries/query.sql

@@ -1,34 +1,6 @@
--- name: CreateIdentifier :one
-INSERT INTO identifiers (slug)
-VALUES ($1)
-RETURNING id, slug, created_at, updated_at;
-
--- name: GetIdentifierById :one
-SELECT id, slug, created_at, updated_at
-FROM identifiers
-WHERE id = $1;
-
--- name: GetIdentifierBySlug :one
-SELECT id, slug, created_at, updated_at
-FROM identifiers
-WHERE slug = $1;
-
--- name: ListIdentifiers :many
-SELECT id, slug, created_at, updated_at
-FROM identifiers
-ORDER BY created_at DESC
-LIMIT $1 OFFSET $2;
-
--- name: DeleteIdentifier :exec
-DELETE FROM identifiers
-WHERE id = $1;
-
--- name: UpdateIdentifierSlug :one
-UPDATE identifiers
-SET slug = $2, updated_at = NOW()
-WHERE id = $1
-RETURNING id, slug, created_at, updated_at;
-
--- name: CountIdentifiers :one
-SELECT COUNT(*) FROM identifiers;
-
+-- name: UserExistsByIdentifier :one
+SELECT EXISTS (
+    SELECT 1
+    FROM public."user"
+    WHERE identifier = $1
+) AS exists;