[MM-47542] Extend Plugin API (#21446)

* Extend Plugin API

* Use Error, NoError in tests

* Address suggestions

* Simplify code

* Add new line

* Add featureflag and GetCollectionMetadataByIds hook

* Add enter at the end of file

* make build-templates

* Fix test

* Fix GetCollectionMetadataByIds ret type

* Add GetTopicMetadataByIds hook

* Add log

* Extract i18n

* Add experimental notice on hooks

* Update model/feature_flags.go

* Swap user to userId

* Change userId to userID

Co-authored-by: Jesse Hallam <jesse.hallam@gmail.com>

model/feature_flags.go

@@ -81,6 +81,8 @@ type FeatureFlags struct {
 
 	// A/B Test on reduced onboarding task list item
 	ReduceOnBoardingTaskList bool
+
+	ThreadsEverywhere bool
 }
 
 func (f *FeatureFlags) SetDefaults() {
@@ -111,6 +113,7 @@ func (f *FeatureFlags) SetDefaults() {
 	f.PeopleProduct = false
 	f.AnnualSubscription = false
 	f.ReduceOnBoardingTaskList = false
+	f.ThreadsEverywhere = false
 }
 
 func (f *FeatureFlags) Plugins() map[string]string {