LetsEncrypt: Allow to set User-Agent

* Add user_agent and user_agent_comment that directly map to certbot
  arguments of same name.

Author: blami

letsencrypt/DOCS.md

@@ -255,6 +255,25 @@ When you specify a custom ACME server, the *Dry Run* and *Issue test certificate
 
 </details>
 
+<details>
+  <summary>Change User-Agent</summary>
+
+For auditing purposes it might be useful to override User-Agent HTTP header that addon and its providers send when making requests.
+
+Setting field `user_agent` will completely override value of User-Agent:
+
+  ```yaml
+  user_agent: "HomeAssistant"
+  ```
+
+Setting field `user_agent_comment` will add value to CertBot User-Agent header:
+
+  ```yaml
+  user_agent_comment: "HomeAssistant"
+  ```
+
+</details>
+
 <details>
   <summary>Selecting the Key Type</summary>
 

letsencrypt/config.yaml

@@ -169,6 +169,8 @@ schema:
   elliptic_curve: list(secp256r1|secp384r1)?
   acme_server: url?
   acme_root_ca_cert: str?
+  user_agent: str?
+  user_agent_comment: str?
   verbose: bool?
   dry_run: bool?
   test_cert: bool?

letsencrypt/rootfs/etc/services.d/lets-encrypt/run

@@ -19,6 +19,8 @@ CHALLENGE=$(bashio::config 'challenge')
 DNS_PROVIDER=$(bashio::config 'dns.provider')
 ACME_SERVER=$(bashio::config 'acme_server')
 ACME_ROOT_CA_CERT=$(bashio::config 'acme_root_ca_cert')
+USER_AGENT=$(bashio::config 'user_agent')
+USER_AGENT_COMMENT=$(bashio::config 'user_agent_comment')
 EAB_KID=$(bashio::config 'eab_kid')
 EAB_HMAC_KEY=$(bashio::config 'eab_hmac_key')
 DRY_RUN=$(bashio::config 'dry_run')
@@ -354,6 +356,14 @@ if [ "${VERBOSE}" = "true" ]; then
     ADDITIONAL_ARGS+=("-vvv")
 fi
 
+# Add user agent if set
+if [ -n "${USER_AGENT}" ]; then
+    ADDITIONAL_ARGS+=("--user-agent" "${USER_AGENT}")
+fi
+if [ -n "${USER_AGENT_COMMENT}" ]; then
+    ADDITIONAL_ARGS+=("--user-agent-comment" "${USER_AGENT_COMMENT}") 
+fi
+
 # Gather all domains into a plaintext file
 DOMAIN_ARR=()
 for line in $DOMAINS; do