MM-29726 Allow disabling link previews from certain domains (#16869)

* Add field to config model

Config option for disabling link previews for given domains.

* Refactor functions and corresponding tests

* Expand logic for link preview

Newly added isLinkAllowedForPreview function determines whether a link
should display a preview. It gets corresponding config values consisting
of comma separated domain values, normalizes them and checks for
matches.

* Create tests for link preview restriction

* Fix formatting issue

* Add test cases where images are expected

* Apply suggestions from code review

Co-authored-by: Ibrahim Serdar Acikgoz <serdaracikgoz86@gmail.com>

* Apply remaining code suggestions

* Add RestrictLinkPreviews value to telemetries

Co-authored-by: Ibrahim Serdar Acikgoz <serdaracikgoz86@gmail.com>
Co-authored-by: Mattermod <mattermod@users.noreply.github.com>
Co-authored-by: Harrison Healey <harrisonmhealey@gmail.com>

services/telemetry/telemetry.go

@@ -440,6 +440,7 @@ func (ts *TelemetryService) trackConfig() {
 		"thread_auto_follow":                                      *cfg.ServiceSettings.ThreadAutoFollow,
 		"enable_link_previews":                                    *cfg.ServiceSettings.EnableLinkPreviews,
 		"enable_file_search":                                      *cfg.ServiceSettings.EnableFileSearch,
+		"restrict_link_previews":                                  isDefault(*cfg.ServiceSettings.RestrictLinkPreviews, ""),
 	})
 
 	ts.sendTelemetry(TrackConfigTeam, map[string]interface{}{