Correct primary key on pipeline_refs table

database/db.go

@@ -181,10 +181,12 @@ CREATE TABLE runners (
 );
 
 CREATE TABLE pipeline_refs (
-	name			TEXT PRIMARY KEY NOT NULL,
+	name			TEXT NOT NULL,
 	pipeline_id 	UUID NOT NULL,
 	hash			TEXT NOT NULL,
 
+    PRIMARY KEY(name, pipeline_id),
+
     CONSTRAINT fk_pipeline_id
         FOREIGN KEY(pipeline_id)
             REFERENCES pipelines(id)