Basic Prometheus metrics for API requests #3051

Job	Run time
Build frontend e2e test image	3m 57s
Build backend e2e test image	1m 41s
Build frontend unit test image	1m 39s
lint_core	17s
Lint mwdb-core web sources	50s
Build mwdb-core core image	2m 59s
Build mwdb-core web image	1m 25s
Perform frontend unit tests	47s
Perform backend e2e tests	4m 15s
Perform frontend e2e tests	3m 58s
Push test images on Docker Hub	0s
Push images on Docker Hub	0s
	21m 48s

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