docs: def search_allowed_users_for_issue(self, user, issueKey=None, projectKey=None, startAt=0, maxResults=50):
          """Get a list of user Resources that match a username string and have browse permission for the issue or project.
  
          :param user: a string to match usernames against.
          :type user: str
          :param issueKey: find users with browse permission for this issue.
          :type issueKey: Optional[str]
          :param projectKey: find users with browse permission for this project.
          :type projectKey: Optional[str]
          :param startAt: index of the first user to return. (Default: 0)
          :type startAt: int
          :param maxResults: maximum number of users to return.
                  If maxResults evaluates as False, it will try to get all items in batches. (Default: 50)
          :type maxResults: int
          """
          params = {
              'username': user}
          if issueKey is not None:
              params['issueKey'] = issueKey
          if projectKey is not None:
              params['projectKey'] = projectKey
          return self._fetch_pages(User, None, 'user/viewissue/search', startAt, maxResults, params)