Certs: Website Changes

[georgekarrv]

• [x] Allow to download a CSR without sending an email by providing an deliveryMethod=json query parameter to the current endpoint
• [x] Endpoint should respond with JSON:

{
  "csr": "base-64-value"
}

[roperzh]

This was merged directly into main. I tested the deployed changes using the old fleetctl generate mdm-apple workflow to make sure it's still working for existing fleet instances and I successfully received the CSR via email and used it to generate a certificate

[fleet-release]

No email required, Data as JSON now flows, Like a quiet stream.