Add read-only support for the Group epic boards API (/groups/:id/epic_boards) #3460

--- a/group_epic_boards.go
+++ b/group_epic_boards.go
@@ -0,0 +1,104 @@
...
+// GroupEpicBoard represents a GitLab group epic board.
+//
+// GitLab API docs:
+// https://docs.gitlab.com/ee/api/group_epic_boards.html
+type GroupEpicBoard struct {
+	ID     int             `json:"id"`
+	Name   string          `json:"name"`
+	Group  *Group          `json:"group"`
+	Labels []*LabelDetails `json:"labels"`
+	Lists  []*BoardList    `json:"lists"`
+}
...
+func (s *GroupEpicBoardsService) ListGroupEpicBoards(gid interface{}, opt *ListGroupEpicBoardsOptions, options ...RequestOptionFunc) ([]*GroupEpicBoard, *Response, error) {
+	group, err := parseID(gid)
+	if err != nil {
+		return nil, nil, err
+	}
+	u := fmt.Sprintf("groups/%s/epic_boards", PathEscape(group))
...
+func (s *GroupEpicBoardsService) GetGroupEpicBoard(gid interface{}, board int, options ...RequestOptionFunc) (*GroupEpicBoard, *Response, error) {
+	group, err := parseID(gid)
+	if err != nil {
+		return nil, nil, err
+	}
+	u := fmt.Sprintf("groups/%s/epic_boards/%d", PathEscape(group), board)

diff --git a/docs/gl_objects/boards.rst b/docs/gl_objects/boards.rst
--- a/docs/gl_objects/boards.rst
+++ b/docs/gl_objects/boards.rst
@@ -102,3 +102,39 @@ set it at the given position and move the following lists up a position::
 Delete a list::
 
     b_list.delete()
+
+Group epic boards
+=================
+
+Epic boards show the epics of a group, organized in lists. Only read access
+is available through the API.
+
+Reference
+---------
+
+* v4 API:
+
+  + :class:`gitlab.v4.objects.GroupEpicBoard`
+  + :class:`gitlab.v4.objects.GroupEpicBoardManager`
+  + :attr:`gitlab.v4.objects.Group.epicboards`
+  + :class:`gitlab.v4.objects.GroupEpicBoardList`
+  + :class:`gitlab.v4.objects.GroupEpicBoardListManager`
+  + :attr:`gitlab.v4.objects.GroupEpicBoard.lists`
+
+* GitLab API: https://docs.gitlab.com/api/group_epic_boards (EE feature)
+
+Examples
+--------
+
+List the epic boards of a group::
+
+    boards = group.epicboards.list(get_all=True)
+
+Get a single epic board::
+
+    board = group.epicboards.get(board_id)
+
+List the lists of an epic board, or get a single list::
+
+    b_lists = board.lists.list(get_all=True)
+    b_list = board.lists.get(list_id)
diff --git a/gitlab/v4/objects/boards.py b/gitlab/v4/objects/boards.py
--- a/gitlab/v4/objects/boards.py
+++ b/gitlab/v4/objects/boards.py
@@ -1,5 +1,5 @@
 from gitlab.base import RESTObject
-from gitlab.mixins import CRUDMixin, ObjectDeleteMixin, SaveMixin
+from gitlab.mixins import CRUDMixin, ObjectDeleteMixin, RetrieveMixin, SaveMixin
 from gitlab.types import RequiredOptional
 
 __all__ = [
@@ -7,6 +7,10 @@ __all__ = [
     "GroupBoardListManager",
     "GroupBoard",
     "GroupBoardManager",
+    "GroupEpicBoardList",
+    "GroupEpicBoardListManager",
+    "GroupEpicBoard",
+    "GroupEpicBoardManager",
     "ProjectBoardList",
     "ProjectBoardListManager",
     "ProjectBoard",
@@ -39,6 +43,26 @@ class GroupBoardManager(CRUDMixin[GroupBoard]):
     _create_attrs = RequiredOptional(required=("name",))
 
 
+class GroupEpicBoardList(RESTObject):
+    pass
+
+
+class GroupEpicBoardListManager(RetrieveMixin[GroupEpicBoardList]):
+    _path = "/groups/{group_id}/epic_boards/{board_id}/lists"
+    _obj_cls = GroupEpicBoardList
+    _from_parent_attrs = {"group_id": "group_id", "board_id": "id"}
+
+
+class GroupEpicBoard(RESTObject):
+    lists: GroupEpicBoardListManager
+
+
+class GroupEpicBoardManager(RetrieveMixin[GroupEpicBoard]):
+    _path = "/groups/{group_id}/epic_boards"
+    _obj_cls = GroupEpicBoard
+    _from_parent_attrs = {"group_id": "id"}
+
+
 class ProjectBoardList(SaveMixin, ObjectDeleteMixin, RESTObject):
     pass
 
diff --git a/gitlab/v4/objects/groups.py b/gitlab/v4/objects/groups.py
--- a/gitlab/v4/objects/groups.py
+++ b/gitlab/v4/objects/groups.py
@@ -23,7 +23,7 @@ from gitlab.types import RequiredOptional
 from .access_requests import GroupAccessRequestManager  # noqa: F401
 from .audit_events import GroupAuditEventManager  # noqa: F401
 from .badges import GroupBadgeManager  # noqa: F401
-from .boards import GroupBoardManager  # noqa: F401
+from .boards import GroupBoardManager, GroupEpicBoardManager  # noqa: F401
 from .branches import GroupProtectedBranchManager  # noqa: F401
 from .clusters import GroupClusterManager  # noqa: F401
 from .container_registry import GroupRegistryRepositoryManager  # noqa: F401
@@ -84,6 +84,7 @@ class Group(SaveMixin, ObjectDeleteMixin, RESTObject):
     customattributes: GroupCustomAttributeManager
     deploytokens: GroupDeployTokenManager
     descendant_groups: GroupDescendantGroupManager
+    epicboards: GroupEpicBoardManager
     epics: GroupEpicManager
     exports: GroupExportManager
     hooks: GroupHookManager