ACME TTL hint

[iaean]

It would be great if we can support the capability of modern ACME CA to let the client provide a TTL proposal.

We simply using the TTL hint optionally provided by client via CLAIM: https://github.com/dns3l/dns3l/blob/8e30da278d35341a2f21d83ca293be67877b45d7/openapi.yaml#L1055

We are introducing TTL config per ACME provider:

ca:
  providers:
    id:
      type: acme
      minTTL: 3d
      maxTTL: 90d
      defaultTTL: 90d

If CA is not supporting this, hint is silently ignored. Otherwise:

• If there is no hint defaultTTL is used.
• If hint is not between minTTL and maxTTL claiming failed immediately.
• Otherwise TTL hint is passed to CA. If TTL hint is not accepted by CA, we surely accept any cert issued with CA default TTL.