refactor: rewrite proxy plugin in golang

docs/appendices/0.20.0-migration-guide.md

@@ -15,6 +15,19 @@ The following commands were previously deprecated and were removed in this relea
 - `trace`: Use `trace:on` or `trace:off` instead.
 - `ps`: Use `enter` with a container ID instead to run `ps auxww` within a container.
 
+The refactor of the proxy plugin removes the following functions from being sourced in plugins:
+
+- `proxy#get_app_proxy_port_map()`
+- `proxy#list_app_proxy_ports()`
+- `proxy#filter_app_proxy_ports()`
+- `proxy#add_proxy_ports()`
+- `proxy#remove_proxy_ports()`
+- `proxy#set_proxy_ports()`
+
+The informal policy is to allow removal of functions within a `functions` file if they are not used in OSS plugins. Should you be affected by any such removals, please file an issue to expose the functionality via a plugin trigger.
+
 ## Deprecations
 
 - `nginx:show-conf` has been deprecated in favor of `nginx:show-config`.
+- `proxy#is_app_proxy_enabled()` is deprecated in favor of `plugn trigger proxy-is-enabled`
+- `proxy#get_app_proxy_type()` is deprecated in favor of `plugn trigger proxy-type`

docs/development/plugin-triggers.md

@@ -1295,6 +1295,36 @@ set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
 # TODO
 ```
 
+### `proxy-is-enabled`
+
+- Description: Checks if there is a proxy enabled for the app
+- Invoked by:
+- Arguments: `$APP`
+- Example:
+
+```shell
+#!/usr/bin/env bash
+
+set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+
+# TODO
+```
+
+### `proxy-type`
+
+- Description: Returns the proxy type for an app
+- Invoked by:
+- Arguments: `$APP`
+- Example:
+
+```shell
+#!/usr/bin/env bash
+
+set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+
+# TODO
+```
+
 ### `receive-app`
 
 - Description: Allows you to customize what occurs when an app is received. Normally just triggers an app build.