Prometheus: Introduce prometheus backend library (#83952)

* Move files to prometheus-library

* refactor core prometheus to use prometheus-library

* modify client transport options

* mock

* have a type

* import aliases

* rename

* call the right method

* remove unrelated test from the library

* update codeowners

* go work sync

* update go.work.sum

* make swagger-clean && make openapi3-gen

* add promlib to makefile

* remove clilogger

* Export the function

* update unit test

* add prometheus_test.go

* fix mock type

* use mapUtil from grafana-plugin-sdk-go

pkg/promlib/middleware/force_http_get_test.go

@@ -0,0 +1,44 @@
+package middleware
+
+import (
+	"net/http"
+	"testing"
+
+	"github.com/grafana/grafana-plugin-sdk-go/backend"
+	"github.com/grafana/grafana-plugin-sdk-go/backend/httpclient"
+	"github.com/stretchr/testify/require"
+)
+
+func TestEnsureHttpMethodMiddleware(t *testing.T) {
+	t.Run("Name should be correct", func(t *testing.T) {
+		finalRoundTripper := httpclient.RoundTripperFunc(func(req *http.Request) (*http.Response, error) {
+			return &http.Response{StatusCode: http.StatusOK}, nil
+		})
+		mw := ForceHttpGet(backend.NewLoggerWith("logger", "test"))
+		rt := mw.CreateMiddleware(httpclient.Options{}, finalRoundTripper)
+		require.NotNil(t, rt)
+		middlewareName, ok := mw.(httpclient.MiddlewareName)
+		require.True(t, ok)
+		require.Equal(t, "force-http-get", middlewareName.MiddlewareName())
+	})
+
+	t.Run("Should force GET method", func(t *testing.T) {
+		finalRoundTripper := httpclient.RoundTripperFunc(func(req *http.Request) (*http.Response, error) {
+			return &http.Response{StatusCode: http.StatusOK}, nil
+		})
+
+		mw := ForceHttpGet(backend.NewLoggerWith("logger", "test"))
+		rt := mw.CreateMiddleware(httpclient.Options{}, finalRoundTripper)
+		require.NotNil(t, rt)
+
+		req, err := http.NewRequest(http.MethodPost, "http://example.com", nil)
+		require.NoError(t, err)
+		res, err := rt.RoundTrip(req)
+		require.NoError(t, err)
+		require.NotNil(t, res)
+		require.Equal(t, res.StatusCode, http.StatusMethodNotAllowed)
+		if res.Body != nil {
+			require.NoError(t, res.Body.Close())
+		}
+	})
+}