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/api/frontendsettings.go

@@ -240,6 +240,7 @@ func (hs *HTTPServer) getFrontendSettingsMap(c *models.ReqContext) (map[string]i
 		"featureToggles":    hs.Cfg.FeatureToggles,
 		"rendererAvailable": hs.RenderService.IsAvailable(),
 		"http2Enabled":      hs.Cfg.Protocol == setting.HTTP2Scheme,
+		"sentry":            hs.Cfg.Sentry,
 		"marketplaceUrl":    hs.Cfg.MarketplaceURL,
 	}