ACME: save account URL to the state directory.

We already log the URL, but on INFO level and only once.  And while it
is possible to find the URL from private key, the operation is not
trivial.

Let's make this simpler by writing a file named "account.url" to the
state directory whenever the issuer tells us it created a new account.

Fixes #54

Author: bavshin-f5

src/conf/issuer.rs

@@ -33,6 +33,8 @@ use crate::state::certificate::{CertificateContext, CertificateContextInner};
 use crate::state::issuer::{IssuerContext, IssuerState};
 use crate::time::{Time, TimeRange};
 
+pub const ACCOUNT_URL_FILE: &str = "account.url";
+
 const ACCOUNT_KEY_FILE: &str = "account.key";
 const NGX_ACME_DEFAULT_RESOLVER_TIMEOUT: ngx_msec_t = 30000;
 const NGX_CONF_UNSET_FLAG: ngx_flag_t = nginx_sys::NGX_CONF_UNSET as _;

src/lib.rs

@@ -292,6 +292,7 @@ async fn ngx_http_acme_update_certificates_for_issuer(
                         x,
                         issuer.name
                     );
+                    let _ = issuer.write_state_file(conf::issuer::ACCOUNT_URL_FILE, x.as_bytes());
                 }
                 Ok(acme::NewAccountOutput::Found(x)) => {
                     ngx_log_debug!(