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/custom_query_params.go

@@ -0,0 +1,57 @@
+package middleware
+
+import (
+	"net/http"
+	"net/url"
+
+	sdkhttpclient "github.com/grafana/grafana-plugin-sdk-go/backend/httpclient"
+
+	"github.com/grafana/grafana-plugin-sdk-go/backend/log"
+)
+
+const (
+	customQueryParametersMiddlewareName = "prom-custom-query-parameters"
+	customQueryParametersKey            = "customQueryParameters"
+	grafanaDataKey                      = "grafanaData"
+)
+
+func CustomQueryParameters(logger log.Logger) sdkhttpclient.Middleware {
+	return sdkhttpclient.NamedMiddlewareFunc(customQueryParametersMiddlewareName, func(opts sdkhttpclient.Options, next http.RoundTripper) http.RoundTripper {
+		grafanaData, exists := opts.CustomOptions[grafanaDataKey]
+		if !exists {
+			return next
+		}
+
+		data, ok := grafanaData.(map[string]any)
+		if !ok {
+			return next
+		}
+		customQueryParamsVal, exists := data[customQueryParametersKey]
+		if !exists {
+			return next
+		}
+
+		customQueryParams, ok := customQueryParamsVal.(string)
+		if !ok || customQueryParams == "" {
+			return next
+		}
+
+		values, err := url.ParseQuery(customQueryParams)
+		if err != nil {
+			logger.Error("Failed to parse custom query parameters, skipping middleware", "error", err)
+			return next
+		}
+
+		return sdkhttpclient.RoundTripperFunc(func(req *http.Request) (*http.Response, error) {
+			q := req.URL.Query()
+			for k, keyValues := range values {
+				for _, value := range keyValues {
+					q.Add(k, value)
+				}
+			}
+			req.URL.RawQuery = q.Encode()
+
+			return next.RoundTrip(req)
+		})
+	})
+}