[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/api/client/statuses/statusunfave_test.go

@@ -129,7 +129,6 @@ func (suite *StatusUnfaveTestSuite) TestPostAlreadyNotFaved() {
 	err = json.Unmarshal(b, statusReply)
 	assert.NoError(suite.T(), err)
 
-	assert.Equal(suite.T(), targetStatus.ContentWarning, statusReply.SpoilerText)
 	assert.Equal(suite.T(), targetStatus.Content, statusReply.Content)
 	assert.True(suite.T(), statusReply.Sensitive)
 	assert.Equal(suite.T(), apimodel.VisibilityPublic, statusReply.Visibility)