fix(gitlab): Copy immutable querydict before modifying (#59130)

In this PR #58679, I refactored
some code. I didn't realize that Django query parameters are stored as a
QueryDict which is immutable.

To fix it I make a copy before modifying. Also change argument types
from `MutableMapping` -> `Mapping`

### In Action


https://github.com/getsentry/sentry/assets/67301797/e0af4d2c-8a84-480c-8071-699987b95ad6

Resolves #59092

Author: schew2381

src/sentry/integrations/gitlab/issues.py

@@ -1,5 +1,5 @@
 import re
-from typing import Any, Dict, List, MutableMapping, Sequence
+from typing import Any, Dict, List, Mapping, Sequence
 
 from django.urls import reverse
 
@@ -24,11 +24,13 @@ def get_issue_url(self, key):
     def get_persisted_default_config_fields(self) -> Sequence[str]:
         return ["project"]
 
-    def get_projects_and_default(self, group: Group, params: MutableMapping[str, Any], **kwargs):
+    def get_projects_and_default(self, group: Group, params: Mapping[str, Any], **kwargs):
         defaults = self.get_project_defaults(group.project_id)
 
         # XXX: In GitLab repositories are called projects but get_repository_choices
         # expects the param to be called 'repo', so we need to rename it here.
+        # Django QueryDicts are immutable, so we need to copy it first.
+        params = params.copy()
         params["repo"] = params.get("project") or defaults.get("project")
 
         default_project, project_choices = self.get_repository_choices(group, params, **kwargs)

src/sentry/integrations/mixins/issues.py

@@ -4,7 +4,7 @@
 import logging
 from collections import defaultdict
 from copy import deepcopy
-from typing import Any, ClassVar, Dict, List, Mapping, MutableMapping, Sequence
+from typing import Any, ClassVar, Dict, List, Mapping, Sequence
 
 from sentry.integrations.utils import where_should_sync
 from sentry.models.group import Group
@@ -268,7 +268,7 @@ def get_issue_display_name(self, external_issue):
         """
         return ""
 
-    def get_repository_choices(self, group: Group, params: MutableMapping[str, Any], **kwargs):
+    def get_repository_choices(self, group: Group, params: Mapping[str, Any], **kwargs):
         """
         Returns the default repository and a set/subset of repositories of associated with the installation
         """