Fixes editing and pinning a post (#19425)

PR https://github.com/mattermost/mattermost-server/pull/19404 fixed the
replies on posts by casting StringArray to a string.

This PR fixes editing and pinning a post by casting StringArray, and
StringInterface to a string as well.

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

model/utils.go

@@ -80,7 +80,7 @@ func (sa StringArray) Value() (driver.Value, error) {
 	if err != nil {
 		return nil, err
 	}
-	// non utf8 characters are not supported
+	// non utf8 characters are not supported https://mattermost.atlassian.net/browse/MM-41066
 	return string(j), err
 }
 
@@ -124,7 +124,12 @@ func (m *StringMap) Scan(value interface{}) error {
 
 // Value converts StringMap to database value
 func (m StringMap) Value() (driver.Value, error) {
-	return json.Marshal(m)
+	j, err := json.Marshal(m)
+	if err != nil {
+		return nil, err
+	}
+	// non utf8 characters are not supported https://mattermost.atlassian.net/browse/MM-41066
+	return string(j), err
 }
 
 func (si *StringInterface) Scan(value interface{}) error {
@@ -147,7 +152,12 @@ func (si *StringInterface) Scan(value interface{}) error {
 
 // Value converts StringInterface to database value
 func (si StringInterface) Value() (driver.Value, error) {
-	return json.Marshal(si)
+	j, err := json.Marshal(si)
+	if err != nil {
+		return nil, err
+	}
+	// non utf8 characters are not supported https://mattermost.atlassian.net/browse/MM-41066
+	return string(j), err
 }
 
 var translateFunc i18n.TranslateFunc