feat: manage vector container via compose

Using compose instead of manual docker calls allows folks to customize the vector container by using a custom compose.yml template file. This opens us up to more customizations while aligning container management with how we do other external containers (such as for the proxy plugins).

Refs #5784

docs/development/plugin-triggers.md

@@ -2950,3 +2950,18 @@ main() {
 
 main "$@"
 ```
+
+### `vector-template-source`
+
+- Description: Retrieves an alternative template for the vector compose config
+- Invoked by: caddy-vhosts
+- Arguments:
+- Example:
+
+```shell
+#!/usr/bin/env bash
+
+set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+
+# TODO
+```