make: add integration tests to docker_test; add cleanup

Makefile

@@ -140,4 +140,11 @@ build_docker_db: check
 .PHONY: test_docker_db
 test_docker_db: check
 	docker build -t ${DOCKER_NAMESPACE}/db:build-${COMMIT_SHA} ${REPO}
-	docker run ${DOCKER_NAMESPACE}/db:build-${COMMIT_SHA} glide nv | xargs go test
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+	docker run ${DOCKER_NAMESPACE}/db:build-${COMMIT_SHA} glide nv | xargs go test -tags integration
+
+### Clean up
+
+# clean removes the target folder containing build artefacts
+.PHONY: clean
+clean:
+	-rm -r ./target 
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