feat: add AllPages pagination helper

pagination.go

@@ -0,0 +1,34 @@
+package gitlab
+
+// AllPages can be used to fetch all pages of a paginated resource, e.g.: (assuming gl is a gitlab client instance)
+//
+//	allUsers, err := gitlab.AllPages(gl.Users.List, nil)
+//
+// It is also possible to specify additional pagination parameters:
+//
+//	mrs, err := gitlab.AllPages(gl.MergeRequests.ListMergeRequests, &gitlab.ListMergeRequestsOptions{
+//		ListOptions: gitlab.ListOptions{
+//			PerPage:    100,
+//			Pagination: "keyset",
+//			OrderBy:    "created_at",
+//		},
+//	})
+func AllPages[O, T any](f Paginatable[O, T], opt *O) ([]*T, error) {
+	all := make([]*T, 0)
+	nextLink := ""
+	for {
+		page, resp, err := f(opt, WithKeysetPaginationParameters(nextLink))
+		if err != nil {
+			return nil, err
+		}
+		all = append(all, page...)
+		if resp.NextLink == "" {
+			break
+		}
+		nextLink = resp.NextLink
+	}
+	return all, nil
+}
+
+// Paginatable is the type that is implemented by all functions used to paginated content.
+type Paginatable[O, T any] func(*O, ...RequestOptionFunc) ([]*T, *Response, error)