[feature] Parse content warning to HTML, serialize via client API as plaintext (#3876)

* [feature] Parse content warning as HTML, serialize via API to plaintext

* tidy up some cruft

* whoops

* oops

* i'm da joker baybee

* clemency muy lorde

* rename some of the text functions for clarity

* jiggle the opts

* fiddle de deee

* hopefully the last test fix i ever have to do in my beautiful life

internal/cache/size.go

@@ -666,6 +666,7 @@ func sizeofStatus() uintptr {
 		BoostOfID:                exampleID,
 		BoostOfAccountID:         exampleID,
 		ContentWarning:           exampleUsername, // similar length
+		ContentWarningText:       exampleUsername, // similar length
 		Visibility:               gtsmodel.VisibilityPublic,
 		Sensitive:                func() *bool { ok := false; return &ok }(),
 		Language:                 "en",