Adds enum certificate_source to pages_domains table
with default manually_uploaded
Mark certificates as 'gitlab_provided'
if the were obtained through Let's Encrypt
Mark certificates as 'user_provided' if they were uploaded through
controller or api
Only show private key in domain edit form if it is 'user_provided'
Only show LetsEncrypt option if is enabled by application settings
(and feature flag)
Refactor and fix some specs to match new logic
Don't show Let's Encrypt certificates as well
Extract acme double to helper
Create ACME challanges for pages domains
* Create order & challange through API
* save them to database
* request challenge validation
We're saving order and challenge as one entity,
that wouldn't be correct if we would order certificates for
several domains simultaneously, but we always order certificate
per domain
Add controller for processing acme challenges redirected from pages
Don't save acme challenge url - we don't use it
Validate acme challenge attributes
Encrypt private_key in acme orders
