[MM-47378] Respond with bad requests for wrong query parameters 'roles' in getUsers (#21569)

* Respond with bad requests for wrong query parameters in roles

* Revert "Respond with bad requests for wrong query parameters in roles"

This reverts commit d8374d94e0b1f61ad445127010f9780475c48d1a.

* Add GetUser client function to query with channel_id and roles

* Return bad parameters error on invalid roles

* Make client function generic, lint fixes

* i18n strings addition

* Validate 'role', add stricter check for comma separated roles

model/client4.go

@@ -1060,6 +1060,24 @@ func (c *Client4) GetUsers(page int, perPage int, etag string) ([]*User, *Respon
 	return list, BuildResponse(r), nil
 }
 
+// GetUsersWithChannelRoles returns a page of users on the system. Page counting starts at 0.
+func (c *Client4) GetUsersWithCustomQueryParameters(page int, perPage int, queryParameters, etag string) ([]*User, *Response, error) {
+	query := fmt.Sprintf("?page=%v&per_page=%v&%v", page, perPage, queryParameters)
+	r, err := c.DoAPIGet(c.usersRoute()+query, etag)
+	if err != nil {
+		return nil, BuildResponse(r), err
+	}
+	defer closeBody(r)
+	var list []*User
+	if r.StatusCode == http.StatusNotModified {
+		return list, BuildResponse(r), nil
+	}
+	if err := json.NewDecoder(r.Body).Decode(&list); err != nil {
+		return nil, nil, NewAppError("GetUsers", "api.unmarshal_error", nil, "", http.StatusInternalServerError).Wrap(err)
+	}
+	return list, BuildResponse(r), nil
+}
+
 // GetUsersInTeam returns a page of users on a team. Page counting starts at 0.
 func (c *Client4) GetUsersInTeam(teamId string, page int, perPage int, etag string) ([]*User, *Response, error) {
 	query := fmt.Sprintf("?in_team=%v&page=%v&per_page=%v", teamId, page, perPage)