Issue Summary

Update https://developer.atlassian.com/cloud/jira/platform/webhooks/#variable-substitution-in-the-webhook-url documentation so that it specifies variables for each webhook.

Steps to Reproduce

1. go to https://developer.atlassian.com/cloud/jira/platform/webhooks/#variable-substitution-in-the-webhook-url
2. eg. {issue.id} is not available for issue link related events

Expected Results

Admin can reliably use the variable substitution in webhook url

eg.

Note that variables are only available to a webhook in the context of its registered events. For example, {issue.key} and {issue.id} are available to webhooks registered for events related to issues. 

which is not true eg. for issue link related events

Actual Results

It's not clear if all the described variable substitutions work with all events 

Workaround

Currently there is no known workaround for this behavior. A workaround will be added here when available