feat: 新增群组成员数量统计功能并在接口中返回

实现了群组成员数量统计的接口，包含数据库层统计逻辑，在群组详情、设置等接口中返回实时成员数，同时修复了测试用例中参数空格问题。

server/im_http_test.go

@@ -273,6 +273,7 @@ type testGroupBusinessStore struct {
 	listMembers       []types.GroupMember
 	listMembersOpts   types.GroupMemberListOptions
 	listMembersNext   string
+	membersCounts     map[string]int64
 	updatedSettings   types.GroupSettingsPatch
 	updatedMembers    []types.GroupMemberPatch
 	updatedRoleMode   types.AccessMode
@@ -354,6 +355,13 @@ func (s *testGroupBusinessStore) ListMembers(_ types.TenantID, _ string, opts ty
 	return s.listMembers, s.listMembersNext, nil
 }
 
+func (s *testGroupBusinessStore) MembersCount(_ types.TenantID, _ []string) (map[string]int64, error) {
+	if s.membersCounts == nil {
+		return map[string]int64{}, nil
+	}
+	return s.membersCounts, nil
+}
+
 func (s *testGroupBusinessStore) UpdateMember(_ types.TenantID, topic string, uid types.Uid, patch types.GroupMemberPatch) (*types.GroupMember, error) {
 	if s.updateMemberErr != nil {
 		return nil, s.updateMemberErr
@@ -730,7 +738,7 @@ func (s *testProfilesStore) UpdatePrivacy(_ types.TenantID, uid types.Uid, patch
 	return privacy, nil
 }
 
-func (s *testAppReleaseStore) Latest(platform, channel string) (*types.AppRelease, error) {
+func (s *testAppReleaseStore) Latest(_, platform, channel string) (*types.AppRelease, error) {
 	if s.err != nil {
 		return nil, s.err
 	}