new package: promquery

This implementation originated in Limes and spread into Castellum. It's
time to deduplicate it.

README.md

@@ -17,6 +17,7 @@ reusability. Feel free to add to this.
 * [must](./must) contains convenience functions for quickly exiting on fatal errors without the need for excessive `if err != nil`.
 * [osext](./osext) contains extensions to the standard library package "os", mostly relating to parsing of environment variables.
 * [pluggable](./pluggable) is a tiny plugin factory library, for constructing different objects implementing a common interface based on a configurable type selector.
+* [promquery](./promquery) provides a simplified interface for executing Prometheus queries.
 * [respondwith](./respondwith) contains some helper functions for generating responses in HTTP handlers.
 * [secrets](./secrets) provides convenience functions for working with auth credentials.
 * [sre](./sre) contains a HTTP middleware that emits SRE-related Prometheus metrics.

go.mod

@@ -11,6 +11,7 @@ require (
 	github.com/hashicorp/golang-lru/v2 v2.0.1
 	github.com/lib/pq v1.10.7
 	github.com/prometheus/client_golang v1.14.0
+	github.com/prometheus/common v0.39.0
 	github.com/rabbitmq/amqp091-go v1.5.0
 	github.com/sapcc/go-api-declarations v1.4.2
 	github.com/sergi/go-diff v1.2.0
@@ -23,10 +24,12 @@ require (
 	github.com/cespare/xxhash/v2 v2.1.2 // indirect
 	github.com/golang/protobuf v1.5.2 // indirect
 	github.com/hashicorp/errwrap v1.0.0 // indirect
-	github.com/matttproud/golang_protobuf_extensions v1.0.1 // indirect
+	github.com/json-iterator/go v1.1.12 // indirect
+	github.com/matttproud/golang_protobuf_extensions v1.0.4 // indirect
+	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
+	github.com/modern-go/reflect2 v1.0.2 // indirect
 	github.com/prometheus/client_model v0.3.0 // indirect
-	github.com/prometheus/common v0.37.0 // indirect
 	github.com/prometheus/procfs v0.8.0 // indirect
-	golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a // indirect
+	golang.org/x/sys v0.3.0 // indirect
 	google.golang.org/protobuf v1.28.1 // indirect
 )