Adding upstream version 0.8.9.

Signed-off-by: Daniel Baumann <daniel@debian.org>

docs/services/generic.md

@@ -0,0 +1,76 @@
+# Generic
+The Generic service can be used for any target that is not explicitly supported by Shoutrrr, as long as it
+supports receiving the message via a POST request.
+Usually, this requires customization on the receiving end to interpret the payload that it receives, and might
+not be a viable approach.
+
+Common examples for use with service providers can be found under [examples](../examples/generic.md).
+
+## Custom headers
+You can add additional HTTP headers to your request by adding query variables prefixed with `@` (`@key=value`).
+
+Using 
+```url
+generic://example.com?@acceptLanguage=tlh-Piqd
+```
+would result in the additional header being added:
+
+```http
+Accept-Language: tlh-Piqd
+```
+
+## JSON template
+By using the built in `JSON` template (`template=json`) you can create a generic JSON payload. The keys used for `title` and `message` can be overriden
+by supplying the params/query values `titleKey` and `messageKey`.
+
+!!! example
+    ```json
+    {
+        "title": "Oh no!",
+        "message": "The thing happened and now there is stuff all over the area!"
+    }
+    ```
+
+### Custom data fields
+When using the JSON template, you can add additional key/value pairs to the JSON object by adding query variables prefixed with `$` (`$key=value`).
+
+!!! example
+    Using `generic://example.com?$projection=retroazimuthal` would yield: 
+
+    ```json
+    {
+        "title": "Amazing opportunities!",
+        "message": "New map book available for purchase.",
+        "projection": "retroazimuthal"
+    }
+    ```
+
+## Shortcut URL
+You can just add `generic+` as a prefix to your target URL to use it with the generic service, so
+```url
+https://example.com/api/v1/postStuff
+```
+would become
+```url
+generic+https://example.com/api/v1/postStuff
+```
+
+!!! note
+    Any query variables added to the URL will be escaped so that they can be forwarded to the remote server. That means that you cannot use `?template=json` with the  `generic+https://`, just use `generic://` instead!
+
+## Forwarded query variables
+All query variables that are not listed in the [Query/Param Props](#queryparam_props) section will be
+forwarded to the target endpoint.
+If you need to pass a query variable that _is_ reserved, you can prefix it with an underscore (`_`).
+
+!!! example
+    The URL `generic+https://example.com/api/v1/postStuff?contenttype=text/plain` would send a POST message
+    to `https://example.com/api/v1/postStuff` using the `Content-Type: text/plain` header.
+
+    If instead escaped, `generic+https://example.com/api/v1/postStuff?_contenttype=text/plain` would send a POST message
+    to `https://example.com/api/v1/postStuff?contenttype=text/plain` using the `Content-Type: application/json` header (as it's the default).
+
+
+## URL Format
+
+--8<-- "docs/services/generic/config.md"