Self-hosted in-product purchase (#21804)

* Self-hosted admins can purchase licenses in-app when `ServiceSettings,SelfHostedPurchase` is true (the default)
* Content Security Policy enables loading assets from `js.stripe.com/v3` when `ServiceSettings.SelfHostedPurchase` is true (the default).
* Add `hosted_customer` API subpath
* Add status of SelfHostedPurchase to telemetry config report.
* Support showing admins self-hosted invoices when `ServiceSettings.SelfHostedPurchase` is true (the default)

Co-authored-by: Conor Macpherson <116016004+ConorMacpherson@users.noreply.github.com>

app/app_iface.go

@@ -916,6 +916,7 @@ type AppIface interface {
 	Notification() einterfaces.NotificationInterface
 	NotificationsLog() *mlog.Logger
 	NotifyAndSetWarnMetricAck(warnMetricId string, sender *model.User, forceAck bool, isBot bool) *model.AppError
+	NotifySelfHostedSignupProgress(progress string, userId string)
 	NotifySharedChannelUserUpdate(user *model.User)
 	OpenInteractiveDialog(request model.OpenDialogRequest) *model.AppError
 	OriginChecker() func(*http.Request) bool

app/hosted_customer.go

@@ -0,0 +1,21 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package app
+
+import (
+	"github.com/mattermost/mattermost-server/v6/model"
+)
+
+func (a *App) NotifySelfHostedSignupProgress(progress string, userId string) {
+	// this is an event only the relevant admin should receive.
+	// If there is no progress, there is nothing to report.
+	// If there is no userId, we do not want to mistakenly broadcast to all users.
+	if progress == "" || userId == "" {
+		return
+	}
+	message := model.NewWebSocketEvent(model.WebsocketEventHostedCustomerSignupProgressUpdated, "", "", userId, nil, "")
+	message.Add("progress", progress)
+
+	a.Srv().Platform().Publish(message)
+}

app/opentracing/opentracing_layer.go

@@ -12632,6 +12632,21 @@ func (a *OpenTracingAppLayer) NotifyAndSetWarnMetricAck(warnMetricId string, sen
 	return resultVar0
 }
 
+func (a *OpenTracingAppLayer) NotifySelfHostedSignupProgress(progress string, userId string) {
+	origCtx := a.ctx
+	span, newCtx := tracing.StartSpanWithParentByContext(a.ctx, "app.NotifySelfHostedSignupProgress")
+
+	a.ctx = newCtx
+	a.app.Srv().Store().SetContext(newCtx)
+	defer func() {
+		a.app.Srv().Store().SetContext(origCtx)
+		a.ctx = origCtx
+	}()
+
+	defer span.Finish()
+	a.app.NotifySelfHostedSignupProgress(progress, userId)
+}
+
 func (a *OpenTracingAppLayer) NotifySessionsExpired() error {
 	origCtx := a.ctx
 	span, newCtx := tracing.StartSpanWithParentByContext(a.ctx, "app.NotifySessionsExpired")