feat: add cloudflare docs and note for godaddy (#1628)

Closes #1612
And Godaddy's "feature"

doc/source/deploy/certificates.rst

@@ -176,6 +176,25 @@ following configuration:
    You'll need to make sure that your AWS credentials have the correct
    permissions to update the Route53 zone.
 
+Cloudflare
+**********
+
+If you are using Cloudflare to host the DNS for your domains, you can use the
+following configuration:
+
+.. code-block:: yaml
+
+  cluster_issuer_acme_email: [email protected]
+  cluster_issuer_acme_solver: cloudflare
+  cluster_issuer_acme_cloudflare_api_token: <CLOUDFLARE_API_TOKEN>
+
+If Cloudflare's account name is different from ACME Issuer's email address
+then also set:
+
+.. code-block:: yaml
+
+  cluster_issuer_acme_cloudflare_email: [email protected]
+
 GoDaddy
 *******
 
@@ -190,6 +209,12 @@ configuration which depends on
   cluster_issuer_acme_godaddy_api_key: <GODADDY_API_KEY>
   cluster_issuer_acme_godaddy_secret_key: <GODADDY_SECRET_KEY>
 
+.. note::
+
+   GoDaddy DNS API has some limitations. To use it you need:
+    - Accounts with 10 or more domains
+    - Accounts with a Discount Domain Club subscription
+
 Infoblox
 ********