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/client4.go

@@ -8558,6 +8558,72 @@ func (c *Client4) GetNewTeamMembersSince(teamID string, timeRange string, page i
 	return newTeamMembersList, BuildResponse(r), nil
 }
 
+func (c *Client4) SelfHostedSignupAvailable() (*Response, error) {
+	r, err := c.DoAPIGet(c.hostedCustomerRoute()+"/signup_available", "")
+
+	if err != nil {
+		return BuildResponse(r), err
+	}
+	defer closeBody(r)
+
+	return BuildResponse(r), nil
+}
+
+func (c *Client4) SelfHostedSignupCustomer(form *SelfHostedCustomerForm) (*Response, *SelfHostedSignupCustomerResponse, error) {
+	payloadBytes, err := json.Marshal(form)
+	if err != nil {
+		return nil, nil, NewAppError("SelfHostedSignupCustomer", "api.marshal_error", nil, "", http.StatusInternalServerError).Wrap(err)
+	}
+
+	r, err := c.DoAPIPost(c.hostedCustomerRoute()+"/customer", string(payloadBytes))
+
+	if err != nil {
+		return BuildResponse(r), nil, err
+	}
+	data, err := io.ReadAll(r.Body)
+	if err != nil {
+		return BuildResponse(r), nil, err
+	}
+	defer closeBody(r)
+
+	response := SelfHostedSignupCustomerResponse{}
+	err = json.Unmarshal(data, &response)
+	if err != nil {
+		return BuildResponse(r), nil, err
+	}
+
+	return BuildResponse(r), &response, nil
+}
+
+func (c *Client4) SelfHostedSignupConfirm(form *SelfHostedConfirmPaymentMethodRequest) (*Response, *SelfHostedSignupConfirmClientResponse, error) {
+	payloadBytes, err := json.Marshal(form)
+	if err != nil {
+		return nil, nil, NewAppError("SelfHostedSignupConfirm", "api.marshal_error", nil, "", http.StatusInternalServerError).Wrap(err)
+	}
+
+	r, err := c.DoAPIPost(c.hostedCustomerRoute()+"/confirm", string(payloadBytes))
+
+	if err != nil {
+		return BuildResponse(r), nil, err
+	}
+
+	data, err := io.ReadAll(r.Body)
+	if err != nil {
+		return BuildResponse(r), nil, err
+	}
+	defer closeBody(r)
+
+	response := SelfHostedSignupConfirmClientResponse{}
+	err = json.Unmarshal(data, &response)
+	if err != nil {
+		return BuildResponse(r), nil, err
+	}
+
+	defer closeBody(r)
+
+	return BuildResponse(r), &response, nil
+}
+
 func (c *Client4) GetPostInfo(postId string) (*PostInfo, *Response, error) {
 	r, err := c.DoAPIGet(c.postRoute(postId)+"/info", "")
 	if err != nil {