Experiment with addons

Addons allow to execute external programs in some context inside
docspell. Currently it is possible to run them after processing files.
Addons are provided by URLs to zip files.

modules/restserver/src/main/resources/reference.conf

@@ -462,5 +462,39 @@ docspell.server {
          }
       }
     }
+
+    addons = {
+      enabled = false
+
+      # Whether installing addons requiring network should be allowed
+      # or not.
+      allow-impure = true
+
+      # Define patterns of urls that are allowed to install addons
+      # from.
+      #
+      # A pattern is compared against an URL by comparing three parts
+      # of an URL via globs: scheme, host and path.
+      #
+      # You can use '*' (0 or more) and '?' (one) as wildcards in each
+      # part. For example:
+      #
+      #   https://*.mydomain.com/projects/*
+      #   *s://gitea.mydomain/*
+      #
+      # A hostname is separated by dots and the path by a slash. A '*'
+      # in a pattern means to match one or more characters. The path
+      # pattern is always matching the given prefix. So /a/b/* matches
+      # /a/b/c and /a/b/c/d and all other sub-paths.
+      #
+      # Multiple patterns can be defined va a comma separated string
+      # or as an array. An empty string matches no URL, while the
+      # special pattern '*' all by itself means to match every URL.
+      allowed-urls = "*"
+
+      # Same as `allowed-urls` but a match here means do deny addons
+      # from this url.
+      denied-urls = ""
+    }
   }
 }