models: change edit permissions for comments

Change patch comments' edit permissions to match that of the patch
associated with the comment (i.e. patch author, project maintainers, and
delegate) and add permissions for both patch and cover comment authors
to be able to change the `addressed` status of comments as well. For
cover comments, add permissions to edit for cover submitter and project
maintainers.

Signed-off-by: Raxel Gutierrez <raxel@google.com>
Signed-off-by: Daniel Axtens <dja@axtens.net>

Author: Raxel Gutierrez

patchwork/models.py

@@ -675,6 +675,20 @@ def get_absolute_url(self):
         return reverse('comment-redirect', kwargs={'comment_id': self.id})
 
     def is_editable(self, user):
+        if not user.is_authenticated:
+            return False
+
+        # user submitted comment
+        if user == self.submitter.user:
+            return True
+
+        # user submitted cover letter
+        if user == self.cover.submitter.user:
+            return True
+
+        # user is project maintainer
+        if self.cover.project.is_editable(user):
+            return True
         return False
 
     class Meta:
@@ -720,7 +734,9 @@ def delete(self, *args, **kwargs):
         self.patch.refresh_tag_counts()
 
     def is_editable(self, user):
-        return False
+        if user == self.submitter.user:
+            return True
+        return self.patch.is_editable(user)
 
     class Meta:
         ordering = ['date']