fix(acme) api url include /directory by default (#25)

README.md

@@ -90,7 +90,7 @@ $ curl http://localhost:8001/acme -XPATCH
 Name                | Required   | Default | Description
 -------------------:|------------|------------|------------
 config.account_email| Yes        |            | The account identifier, can be reused in different plugin instance.
-config.api_uri      |            |  `"https://acme-v02.api.letsencrypt.org"`   | The ACMEv2 API endpoint to use, the url should only contain root path. User might use [Let's Encrypt staging environemnt](https://letsencrypt.org/docs/staging-environment/)(`https://acme-staging-v02.api.letsencrypt.org`) during testing. Kong doesn't automatically delete staging certificates, if you use same domain to test and use in production, you will need to delete those certificates manaully after test.
+config.api_uri      |            |  `"https://acme-v02.api.letsencrypt.org/directory"`   | The ACMEv2 API endpoint to use, the url should only contain root path. User might use [Let's Encrypt staging environemnt](https://letsencrypt.org/docs/staging-environment/)(`https://acme-staging-v02.api.letsencrypt.org/directory`) during testing. Kong doesn't automatically delete staging certificates, if you use same domain to test and use in production, you will need to delete those certificates manaully after test.
 config.cert_type    |            |  `"rsa"`   | The certificate type to create, choice of `"rsa"` for RSA certificate or `"ecc"` for EC certificate.
 config.domains      |            | `[]`       | The list of domains to create certificate for. To match subdomains under `example.com`, use `*.example.com`. Regex pattern is not supported. Note this config is only used to match domains, not to specify the Common Name or Subject Alternative Name to create certifcates; each domain will have its own certificate.
 config.renew_threshold_days|     |  `14`      | Days before expire to renew the certificate.

kong/plugins/acme/schema.lua

@@ -49,7 +49,7 @@ local schema = {
           match = "%w*%p*@+%w*%.?%w*",
           required = true,
         }, },
-        { api_uri = typedefs.url({ default = "https://acme-v02.api.letsencrypt.org" }),
+        { api_uri = typedefs.url({ default = "https://acme-v02.api.letsencrypt.org/directory" }),
         },
         { tos_accepted = {
           type = "boolean",