Moved certrbot plugin list to backend

frontend doesn't include when building in react version
adds swagger for existing dns-providers endpoint

backend/certbot/README.md

@@ -0,0 +1,21 @@
+# Certbot dns-plugins
+
+This file contains info about available Certbot DNS plugins.
+This only works for plugins which use the standard argument structure, so:
+--authenticator <plugin-name> --<plugin-name>-credentials <FILE> --<plugin-name>-propagation-seconds <number>
+
+File Structure:
+
+```json
+{
+  "cloudflare": {
+    "display_name": "Name displayed to the user",
+    "package_name": "Package name in PyPi repo",
+    "version_requirement": "Optional package version requirements (e.g. ==1.3 or >=1.2,<2.0, see https://www.python.org/dev/peps/pep-0440/#version-specifiers)",
+    "dependencies": "Additional dependencies, space separated (as you would pass it to pip install)",
+    "credentials": "Template of the credentials file",
+    "full_plugin_name": "The full plugin name as used in the commandline with certbot, e.g. 'dns-njalla'"
+  },
+  ...
+}
+```