integrations: Move get_setup_webhook_message to common.py.

Move `get_setup_webhook_message` to
`zerver/lib/webhooks/common.py` so multiple integrations can use this
rather than just those which import `zerver/lib/webhooks/git.py`. Also
added the documentation for this.

templates/zerver/api/incoming-webhooks-overview.md

@@ -106,6 +106,13 @@ below are for a webhook named `MyWebHook`.
   associate it with the function called `api_mywebhook_webhook` in
   `zerver/webhooks/mywebhook/view.py`.
 
+## Common Helpers
+
+* If your integration will receive a test webhook payload, you can use
+  `get_setup_webhook_message` to create our standard message for test payloads.
+  You can import this from `zerver/lib/webhooks/common.py`, and it will generate
+  a message like this: "GitHub webhook is successfully configured! 🎉"
+
 ## General advice
 
 * Consider using our Zulip markup to make the output from your

zerver/lib/webhooks/common.py

@@ -32,10 +32,21 @@ but didn't correctly configure the webhook to send data in the JSON format
 that this integration expects!
 """
 
+SETUP_MESSAGE_TEMPLATE = "{integration} webhook has been successfully configured"
+SETUP_MESSAGE_USER_PART = " by {user_name}"
+
 # Django prefixes all custom HTTP headers with `HTTP_`
 DJANGO_HTTP_PREFIX = "HTTP_"
 
 
+def get_setup_webhook_message(integration: str, user_name: Optional[str] = None) -> str:
+    content = SETUP_MESSAGE_TEMPLATE.format(integration=integration)
+    if user_name:
+        content += SETUP_MESSAGE_USER_PART.format(user_name=user_name)
+    content = f"{content}."
+    return content
+
+
 def notify_bot_owner_about_invalid_json(
     user_profile: UserProfile, webhook_client_name: str
 ) -> None:

zerver/lib/webhooks/git.py

@@ -54,9 +54,6 @@ PULL_REQUEST_OR_ISSUE_MESSAGE_TEMPLATE_WITH_TITLE = (
 PULL_REQUEST_OR_ISSUE_ASSIGNEE_INFO_TEMPLATE = "(assigned to {assignee})"
 PULL_REQUEST_BRANCH_INFO_TEMPLATE = "from `{target}` to `{base}`"
 
-SETUP_MESSAGE_TEMPLATE = "{integration} webhook has been successfully configured"
-SETUP_MESSAGE_USER_PART = " by {user_name}"
-
 CONTENT_MESSAGE_TEMPLATE = "\n~~~ quote\n{message}\n~~~"
 
 COMMITS_COMMENT_MESSAGE_TEMPLATE = "{user_name} {action} on [{sha}]({url})"
@@ -225,14 +222,6 @@ def get_pull_request_event_message(
     return main_message.rstrip()
 
 
-def get_setup_webhook_message(integration: str, user_name: Optional[str] = None) -> str:
-    content = SETUP_MESSAGE_TEMPLATE.format(integration=integration)
-    if user_name:
-        content += SETUP_MESSAGE_USER_PART.format(user_name=user_name)
-    content = f"{content}."
-    return content
-
-
 def get_issue_event_message(
     user_name: str,
     action: str,

zerver/webhooks/github/view.py

@@ -11,6 +11,7 @@ from zerver.lib.response import json_success
 from zerver.lib.webhooks.common import (
     check_send_webhook_message,
     get_http_headers_from_filename,
+    get_setup_webhook_message,
     validate_extract_webhook_http_header,
 )
 from zerver.lib.webhooks.git import (
@@ -23,7 +24,6 @@ from zerver.lib.webhooks.git import (
     get_push_commits_event_message,
     get_push_tag_event_message,
     get_release_event_message,
-    get_setup_webhook_message,
 )
 from zerver.models import UserProfile