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>

model/cloud.go

@@ -290,17 +290,14 @@ type ProductLimits struct {
 	Teams        *TeamsLimits        `json:"teams,omitempty"`
 }
 
-type BootstrapSelfHostedSignupRequest struct {
-	Email string `json:"email"`
-}
-
-type BootstrapSelfHostedSignupResponse struct {
-	Progress string `json:"progress"`
-}
-
-type BootstrapSelfHostedSignupResponseInternal struct {
-	Progress string `json:"progress"`
-	License  string `json:"license"`
+// CreateSubscriptionRequest is the parameters for the API request to create a subscription.
+type CreateSubscriptionRequest struct {
+	ProductID             string   `json:"product_id"`
+	AddOns                []string `json:"add_ons"`
+	Seats                 int      `json:"seats"`
+	Total                 float64  `json:"total"`
+	InternalPurchaseOrder string   `json:"internal_purchase_order"`
+	DiscountID            string   `json:"discount_id"`
 }
 
 func (p *Product) IsYearly() bool {