[bugfix] Store and expose status content type (#3870)

* Add ContentType to internal models

* Add ContentType to API models StatusSource and StatusEdit

* Add helpers to convert between API/internal StatusContentType

* Write status content type on create/edit

* Add migration

* Update API docs

go run github.com/go-swagger/go-swagger/cmd/swagger generate spec --scan-models --exclude-deps --output docs/api/swagger.yaml

* ensure ContentType is updated anywhere Text is

* Update docs, take care of TODOs

* Set ContentType in more places where Text is set

* We don't actually use ContentType on the API status model

* Update StatusSource test

* Remove unused helper function I copied

* Revert change to StatusContentType swagger annotation

I'm going to include this in a follow-on PR instead.

* Add test for updating content type in edits

* Return a value from processContentType instead of modifying the existing status

Fixes an issue that was caught by the test I just added - the recorded edit would be marked with the *new* content type instead of the old one, which is obviously bad

* Add test for handling of statuses with no stored content type

* repurpose an existing test status instead of adding a new one to avoid breaking other tests

* Add test to ensure newly created statuses always have content type saved

* Do include content type on status API model actually

This is mostly important when deleting and redrafting.

The comment on `apimodel.Status.Text` implies that it's not sent except in response to status deletion, but actually this doesn't seem to be the case; it also appears to be present in responses to creations and normal fetches and stuff. So I'm treating `ContentType` the same here.

* Update new tests to check content type on API statuses

* Check content type of API statuses in all tests where text is checked

* update other api tests with status content type field

* Add test ensuring text and content type are returned when deleting a status

* Convert processContentType to free function and remove unused parameter

* check for the correct value in the deletion test

* Be explicit about this test status having an empty content type

* Use omitempty consistently on API models

* clean up the final diff a bit

* one more swagger regen for the road

* Handle nil statuses in processContentType

* Don't pass processContentType the entire edit form, it doesn't need it

* Move processContentType to common.go and use for creation as well

* Remove unused parameters to ContentTypeToAPIContentType

internal/processing/status/common.go

@@ -30,6 +30,7 @@ import (
 	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
 	"github.com/superseriousbusiness/gotosocial/internal/id"
 	"github.com/superseriousbusiness/gotosocial/internal/text"
+	"github.com/superseriousbusiness/gotosocial/internal/typeutils"
 	"github.com/superseriousbusiness/gotosocial/internal/util/xslices"
 	"github.com/superseriousbusiness/gotosocial/internal/validate"
 )
@@ -106,11 +107,39 @@ type statusContent struct {
 	Tags           []*gtsmodel.Tag
 }
 
+// Returns the final content type to use when creating or editing a status.
+func processContentType(
+	requestContentType apimodel.StatusContentType,
+	existingStatus *gtsmodel.Status,
+	accountDefaultContentType string,
+) gtsmodel.StatusContentType {
+	switch {
+	// Content type set in the request, return the new value.
+	case requestContentType != "":
+		return typeutils.APIContentTypeToContentType(requestContentType)
+
+	// No content type in the request, return the existing
+	// status's current content type if we know of one.
+	case existingStatus != nil && existingStatus.ContentType != 0:
+		return existingStatus.ContentType
+
+	// We aren't editing an existing status, or if we are
+	// it's an old one that doesn't have a saved content
+	// type. Use the user's default content type setting.
+	case accountDefaultContentType != "":
+		return typeutils.APIContentTypeToContentType(apimodel.StatusContentType(accountDefaultContentType))
+
+	// uhh.. Fall back to global default.
+	default:
+		return gtsmodel.StatusContentTypeDefault
+	}
+}
+
 func (p *Processor) processContent(
 	ctx context.Context,
 	author *gtsmodel.Account,
 	statusID string,
-	contentType string,
+	contentType gtsmodel.StatusContentType,
 	content string,
 	contentWarning string,
 	language string,
@@ -146,20 +175,14 @@ func (p *Processor) processContent(
 	// function, according to the provided content-type.
 	var format text.FormatFunc
 
-	if contentType == "" {
-		// If content type wasn't specified, use
-		// the author's preferred content-type.
-		contentType = author.Settings.StatusContentType
-	}
-
 	switch contentType {
 
 	// Format status according to text/plain.
-	case "", string(apimodel.StatusContentTypePlain):
+	case gtsmodel.StatusContentTypePlain:
 		format = p.formatter.FromPlain
 
 	// Format status according to text/markdown.
-	case string(apimodel.StatusContentTypeMarkdown):
+	case gtsmodel.StatusContentTypeMarkdown:
 		format = p.formatter.FromMarkdown
 
 	// Unknown.