Add UNIQUE constraint in the states table for the pg backend

internal/backend/remote-state/pg/backend.go

@@ -111,7 +111,7 @@ func (b *Backend) configure(ctx context.Context) error {
 
 		query = `CREATE TABLE IF NOT EXISTS %s.%s (
 			id bigint NOT NULL DEFAULT nextval('public.global_states_id_seq') PRIMARY KEY,
-			name text,
+			name text UNIQUE,
 			data text
 			)`
 		if _, err := db.Exec(fmt.Sprintf(query, b.schemaName, statesTableName)); err != nil {