Finalize hook behaviors

[rdsubhas]

Just adding to make a note / keep track :) Let's try to finalize the hook behavior, just needs to be documented, not necessarily changed or anything :)

Current hooks:

# ingress.cfg
hooks:
  post-render:
    - script 1
    - script 2
    - ...
    - script n 

• Single or multiple scripts: If there are multiple scripts, will they be executed in sequence or parallel, If one of the scripts throws an error will other script still execute or will all hooks stop there, Will the script be directly executed or executed in a shell, Will all the scripts be concatenated and executed in a single shell, Will export A=1 in one script be available in the next script, etc.
• Another option is to have a single script, and letting the user decide whether they want && or ||, i.e. multiple scripts like this:

  post-render: |
    set -ex
    script 1
    script2
    scriptn
  

• Do we pass any environment variables to the hook script, like INGRESSIFY_OUT_FILE or something like that? For the script to read the generated file? Its also fair to keep things simple - and decide that we don't set any env vars, the script is given by user so they already know where the file is written to
• Which cwd will the script be executed in - in same dir as out_file or template
• Do we need to have a shell option in the hooks, which defaults to /bin/sh?