code: @Delete("/metadata/{projectName}/repos/{repoName}/perm/users/{memberId}")
      public CompletableFuture<Revision> removeSpecificUserPermission(@Param("projectName") String projectName,
                                                                      @Param("repoName") String repoName,
                                                                      @Param("memberId") String memberId,
                                                                      Author author) {
          final User member = new User(loginNameNormalizer.apply(urlDecode(memberId)));
          return mds.findPermissions(projectName, repoName, member)
                    .thenCompose(unused -> mds.removePerUserPermission(author, projectName,
                                                                       repoName, member));
      }
docs: DELETE /metadata/{projectName}/repos/{repoName}/perm/users/{memberId}
  
  <p>Removes {@link Permission}s for the specified {@code memberId} from the specified {@code repoName}
  in the specified {@code projectName}.