Add documentation on what configuration is stored in Fastly and what is stored within Magento

[braders]

I am currently working on a new Magento site, and due to our requirements we will be moving the current staging database to the production server before going live. Currently staging and production environments are pointing at independent Fastly instances.

I understand that any changes made to the Fastly configuration eventually become Fastly VCL. However, it looks like some of this data is also stored as configuration within the Magento database: https://github.com/fastly/fastly-magento2/blob/master/etc/adminhtml/system.xml

This makes me unsure what will happen if we copy from staging -> production (or vice-versa) and re-upload the VCL. It's unclear if:

• All the configuration (including things like custom VCL snippets) is stored within Magento, and a fresh VCL will be generated based on the Fastly config values
• All the configuration is held within Fastly, and pulled out of Fastly in order to be shown on the Magento configuration panel
• Some mixture of the above.

I know that the Fastly API credentials will need re-configuring. It's all the other configuration that I'm unsure about.

I think it would be great if the above were documented within the /Documentation folder. I can't believe I'm the first person to have wondered this.