Add custom header and URL query string options to the ntfy publisher

Lets users authenticate ntfy notifications through a reverse proxy or tunnel
(Pangolin, Tailscale, ...) in front of the ntfy instance. Adds three optional,
backward-compatible settings that default to empty and are no-ops when unset:

- NTFY_URL_QUERY_STRING: appended to the request URL (e.g. p_token=...). A
  leading '?' is tolerated, and the value is redacted from error logs / the
  plugin result file since the request URL can carry a secret token.
- NTFY_CUSTOMHEADER_NAME / NTFY_CUSTOMHEADER_VALUE: a custom request header,
  skipped with a warning if it would clobber a built-in header (e.g.
  Authorization) so ntfy's own auth stays intact.

Secret-bearing fields are password-masked in the UI. Addresses #1663.

server/plugins/_publisher_ntfy/config.json

@@ -555,6 +555,78 @@
           "string": "Enable TLS support. Disable if you are using a self-signed certificate."
         }
       ]
+    },
+    {
+      "function": "URL_QUERY_STRING",
+      "type": {
+        "dataType": "string",
+        "elements": [
+          { "elementType": "input", "elementOptions": [{ "type": "password" }], "transformers": [] }
+        ]
+      },
+      "default_value": "",
+      "options": [],
+      "localized": ["name", "description"],
+      "name": [
+        {
+          "language_code": "en_us",
+          "string": "URL query string"
+        }
+      ],
+      "description": [
+        {
+          "language_code": "en_us",
+          "string": "Optional query string appended to the ntfy request URL (e.g. <code>p_token=tokenId.tokenValue</code>). Useful when ntfy is behind a reverse proxy or tunnel (Pangolin, Tailscale, ...) that authenticates via a query parameter. Note: values in the URL may be recorded in proxy/server access logs, so for secrets prefer the custom header below. Leave empty to disable."
+        }
+      ]
+    },
+    {
+      "function": "CUSTOMHEADER_NAME",
+      "type": {
+        "dataType": "string",
+        "elements": [
+          { "elementType": "input", "elementOptions": [], "transformers": [] }
+        ]
+      },
+      "default_value": "",
+      "options": [],
+      "localized": ["name", "description"],
+      "name": [
+        {
+          "language_code": "en_us",
+          "string": "Custom header name"
+        }
+      ],
+      "description": [
+        {
+          "language_code": "en_us",
+          "string": "Optional custom HTTP header name sent with the ntfy request, e.g. to authenticate through a reverse proxy or tunnel. Requires the custom header value to also be set. Leave empty to disable."
+        }
+      ]
+    },
+    {
+      "function": "CUSTOMHEADER_VALUE",
+      "type": {
+        "dataType": "string",
+        "elements": [
+          { "elementType": "input", "elementOptions": [{ "type": "password" }], "transformers": [] }
+        ]
+      },
+      "default_value": "",
+      "options": [],
+      "localized": ["name", "description"],
+      "name": [
+        {
+          "language_code": "en_us",
+          "string": "Custom header value"
+        }
+      ],
+      "description": [
+        {
+          "language_code": "en_us",
+          "string": "Value for the custom HTTP header defined above. Requires the custom header name to also be set. Leave empty to disable."
+        }
+      ]
     }
   ]
 }

server/plugins/_publisher_ntfy/ntfy.py

@@ -2,6 +2,7 @@
 
 import json
 import os
+import re
 import sys
 import requests
 from base64 import b64encode
@@ -94,6 +95,11 @@ def send(html, text):
     user = get_setting_value('NTFY_USER')
     pwd = get_setting_value('NTFY_PASSWORD')
     verify_ssl = get_setting_value('NTFY_VERIFY_SSL')
+    custom_header_name = get_setting_value('NTFY_CUSTOMHEADER_NAME')
+    custom_header_value = get_setting_value('NTFY_CUSTOMHEADER_VALUE')
+    # Strip a leading '?' so both "p_token=..." and "?p_token=..." work; requests
+    # adds the '?' itself, and a leading one would produce a broken "??" in the URL.
+    url_query_string = get_setting_value('NTFY_URL_QUERY_STRING').lstrip('?')
 
     # prepare request headers
     headers = {
@@ -112,6 +118,15 @@ def send(html, text):
         # add authorization header with hash
         headers["Authorization"] = "Basic {}".format(basichash)
 
+    # Optional custom header, e.g. to authenticate through a reverse proxy / tunnel
+    # (Pangolin, Tailscale, ...) sitting in front of the ntfy instance. Skip it if it
+    # would clobber a built-in header (e.g. Authorization) so ntfy auth stays intact.
+    if custom_header_name != '' and custom_header_value != '':
+        if custom_header_name.lower() in {k.lower() for k in headers}:
+            mylog('none', [f'[{pluginName}] ⚠ Custom header "{custom_header_name}" collides with a built-in header; skipping it.'])
+        else:
+            headers[custom_header_name] = custom_header_value
+
     # call NTFY service
     try:
         response = requests.post("{}/{}".format(
@@ -119,6 +134,7 @@ def send(html, text):
             get_setting_value('NTFY_TOPIC')),
             data    = text,
             headers = headers,
+            params  = url_query_string if url_query_string != '' else None,
             verify  = verify_ssl,
             timeout = get_setting_value('NTFY_RUN_TIMEOUT')
         )
@@ -132,9 +148,16 @@ def send(html, text):
             response_text = json.dumps(response.text)
 
     except requests.exceptions.RequestException as e:
-        mylog('none', [f'[{pluginName}] ⚠ ERROR: ', e])
+        # The exception message embeds the request URL, which may include a secret
+        # query string (e.g. a proxy token). Redact the query part before it is
+        # logged and persisted to the plugin result file / shown in the UI.
+        error_text = str(e)
+        if url_query_string != '':
+            error_text = re.sub(r'(\?)\S+', r'\1<redacted>', error_text)
 
-        response_text = e
+        mylog('none', [f'[{pluginName}] ⚠ ERROR: ', error_text])
+
+        response_text = error_text
 
         return response_text, response_status_code