Simplify Logo requirement from users. (#373)

* Simplify Logo requirement from users.
- Only require 1 logo file, instead of a `small` and `large` one.  Just require `logo`.
- Update frontend sso that primary header logo will ALWAYS be owncast logo.
- User's logo will remain in "user content" area.

* Commit updated API documentation

Co-authored-by: Owncast <owncast@owncast.online>

controllers/index.go

@@ -62,7 +62,7 @@ func handleScraperMetadataPage(w http.ResponseWriter, r *http.Request) {
 	if err != nil {
 		log.Panicln(err)
 	}
-	imageURL, err := url.Parse(fmt.Sprintf("http://%s%s", r.Host, config.Config.InstanceDetails.Logo.Large))
+	imageURL, err := url.Parse(fmt.Sprintf("http://%s%s", r.Host, config.Config.InstanceDetails.Logo))
 	if err != nil {
 		log.Panicln(err)
 	}