Change Jira integration to webhook

[Ben-Hodgkiss]

Summary
Following on from the discussions in digital-land/config#1206, we should change our Jira integration to use a JSON webhook rather than an API key.
The pros for this change in approach include:

• API keys must be assigned to personal accounts which is unhelpful when people leave the project
• API keys in Atlassian can only be registered for 365 days before needing changing, requiring us to then remember and update Terraform before the live service falls over
• The webhook approach will provide some cyber assurances as it is only one way
• We can define all the content in Jira so content changes do not need to go through Github developments
• The workflows are created in Jira so once the webhook is built, the ticket creation workflow can be built/edited by non-developers

Some concerns are:

• We will probably not be able to create the import.csv file that is used in the add-data command, however this will soon be deprecated when we launch the Manage Service UI
• We will need to ensure that we put in place key checks so if the webhook location is known then it does not create spam tickets
• The fact the webhook is one way means we will not be able to show the user their ticket number as we currently do

A first step is to create sub-issues on this ticket for the work to be completed. This will be to initially create the webhook alongside the API key generation. Once the webhook is built, we will then create the workflow (in dev) before recreating this in production. We will then turn off the API integration and rely solely on the webhook.