MM-45120: Track team join times. Add API to retrieve new team members since a given time. (#20708)

* MM-45120: Starts tracking team join time. Adds API to retrieve team members who joined after a given time.

* MM-45120: Updates json casing to match model.User.

app/team.go

@@ -2133,3 +2133,16 @@ func (a *App) ClearTeamMembersCache(teamID string) error {
 	}
 	return nil
 }
+
+func (a *App) GetNewTeamMembersSince(c request.CTX, teamID string, opts *model.InsightsOpts) (*model.NewTeamMembersList, int64, *model.AppError) {
+	if !a.Config().FeatureFlags.InsightsEnabled {
+		return nil, 0, model.NewAppError("GetNewTeamMembersSince", "app.insights.feature_disabled", nil, "", http.StatusNotImplemented)
+	}
+
+	ntms, count, err := a.Srv().Store.Team().GetNewTeamMembersSince(teamID, opts.StartUnixMilli, opts.Page*opts.PerPage, opts.PerPage)
+	if err != nil {
+		return nil, 0, model.NewAppError("GetNewTeamMembersSince", "app.post.get_new_team_members_since.app_error", nil, err.Error(), http.StatusInternalServerError)
+	}
+
+	return ntms, count, nil
+}