offline registration with nuxeoctl

Now that JSF UI is deprecated in Nuxeo Server 9.3+, we need to offer a way to register an instance offline using Web UI, but also when using a headless server.

TODO
In nuxeoctl

• Add a [to be determined - command - parameter to nuxeoctl register?] to register your instance offline

• Without parameters command should:

1. Show the following text:

   To register your instance:
   1. Visit [org.nuxeo.connect.url taken from nuxeo.conf]/connect/registerInstance
   2. Select the project on which you want the instance to be registered and copy the technical identifier found below (CTID):
   [CTID]
   3. Press return when you are ready to continue.

2. When pressing return, script prompts for the CLID

   Enter the identifier to register your instance:

   1. If CLID is invalid, error message:

      This identifier is invalid.

      1. prompt again for CLID
   2. If CLID is valid
      1. store the CLID
      2. Display a confirmation message:

         Thank you for registering your instance.
         Your Nuxeo Online Services is valid until [date].

• Command should accept a --clidpath parameter so that people can provide a file as input for the clid
  • when using this parameter, instead of prompting for the CLID nuxeoctl should directly store it, check and
    • display the final message
    • or show

      Invalid clid provided, please try again.

      if clid is invalid.

Example:

>nuxeoctl register --offline