Logging: Log frontend errors (#28073)

* basic frontend  Sentry integration

* backend endpoint to capture sentry events

* WIP!

* log user email for frontend logs

* remove debug logging

* lint fixes

* Fix type exports & property names

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

* additional struct naming fix

* rename log endpoint, config section & interface

* add sentry sample rate to config

* refac to use EchoSrv

* log user id

* backend tests

* tests for SentryEchoBackend

* sentry echo backend tests

* CustomEndpointTransport tests

* Update pkg/api/frontend_logging_test.go

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

* Update conf/defaults.ini

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

* Update pkg/api/frontend_logging_test.go

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

* don't export unnecesasrily

* update go.sum

* get rid of Convey in tests, use stdlib

* add sentry config to sample.ini

* cleanup to set orig logging handler in test

* Apply suggestions from code review

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

* PR feedback changes

* lock sentry version

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

pkg/setting/setting.go

@@ -322,6 +322,9 @@ type Cfg struct {
 	AlertingAnnotationCleanupSetting   AnnotationCleanupSettings
 	DashboardAnnotationCleanupSettings AnnotationCleanupSettings
 	APIAnnotationCleanupSettings       AnnotationCleanupSettings
+
+	// Sentry config
+	Sentry Sentry
 }
 
 // IsExpressionsEnabled returns whether the expressions feature is enabled.
@@ -846,6 +849,7 @@ func (cfg *Cfg) Load(args *CommandLineArgs) error {
 	}
 
 	cfg.readDateFormats()
+	cfg.readSentryConfig()
 
 	return nil
 }