feat: expose certs-set and certs-remove plugin triggers

Adds `certs-set` and `certs-remove` plugin triggers so other plugins can install or remove an app's SSL cert/key pair without shelling out to the `dokku certs:add` / `dokku certs:remove` subcommands. Shared implementations live as `fn-certs-set` and `fn-certs-remove` in `plugins/certs/internal-functions`, with the subcommands and the new triggers calling `verify_app_name` before delegating.

plugins/certs/certs-remove

@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+source "$PLUGIN_CORE_AVAILABLE_PATH/common/functions"
+source "$PLUGIN_AVAILABLE_PATH/certs/internal-functions"
+set -eo pipefail
+[[ $DOKKU_TRACE ]] && set -x
+
+trigger-certs-certs-remove() {
+  declare desc="removes the SSL cert/key pair from an app"
+  declare trigger="certs-remove"
+  declare APP="$1"
+
+  verify_app_name "$APP"
+  fn-certs-remove "$APP"
+}
+
+trigger-certs-certs-remove "$@"