Implement create and get incoming webhook endpoints for APIv4 (#5407)

* Implement POST /hooks/incoming endpoint for APIv4

* Implement GET /hooks/incoming endpoint for APIv4

* Updates per feedback

model/client4.go

@@ -133,6 +133,10 @@ func (c *Client4) GetSystemRoute() string {
 	return fmt.Sprintf("/system")
 }
 
+func (c *Client4) GetIncomingWebhooksRoute() string {
+	return fmt.Sprintf("/hooks/incoming")
+}
+
 func (c *Client4) DoApiGet(url string, etag string) (*http.Response, *AppError) {
 	return c.DoApiRequest(http.MethodGet, url, "", etag)
 }
@@ -775,3 +779,37 @@ func (c *Client4) GetPing() (bool, *Response) {
 		return CheckStatusOK(r), BuildResponse(r)
 	}
 }
+
+// Webhooks Section
+
+// CreateIncomingWebhook creates an incoming webhook for a channel.
+func (c *Client4) CreateIncomingWebhook(hook *IncomingWebhook) (*IncomingWebhook, *Response) {
+	if r, err := c.DoApiPost(c.GetIncomingWebhooksRoute(), hook.ToJson()); err != nil {
+		return nil, &Response{StatusCode: r.StatusCode, Error: err}
+	} else {
+		defer closeBody(r)
+		return IncomingWebhookFromJson(r.Body), BuildResponse(r)
+	}
+}
+
+// GetIncomingWebhooks returns a page of incoming webhooks on the system. Page counting starts at 0.
+func (c *Client4) GetIncomingWebhooks(page int, perPage int, etag string) ([]*IncomingWebhook, *Response) {
+	query := fmt.Sprintf("?page=%v&per_page=%v", page, perPage)
+	if r, err := c.DoApiGet(c.GetIncomingWebhooksRoute()+query, etag); err != nil {
+		return nil, &Response{StatusCode: r.StatusCode, Error: err}
+	} else {
+		defer closeBody(r)
+		return IncomingWebhookListFromJson(r.Body), BuildResponse(r)
+	}
+}
+
+// GetIncomingWebhooksForTeam returns a page of incoming webhooks for a team. Page counting starts at 0.
+func (c *Client4) GetIncomingWebhooksForTeam(teamId string, page int, perPage int, etag string) ([]*IncomingWebhook, *Response) {
+	query := fmt.Sprintf("?page=%v&per_page=%v&team_id=%v", page, perPage, teamId)
+	if r, err := c.DoApiGet(c.GetIncomingWebhooksRoute()+query, etag); err != nil {
+		return nil, &Response{StatusCode: r.StatusCode, Error: err}
+	} else {
+		defer closeBody(r)
+		return IncomingWebhookListFromJson(r.Body), BuildResponse(r)
+	}
+}