Add ability to provide custom metadata

[gusmb]

Enhancement summary

Right now the metadata schema is fixed and dies not allow any custom keys. It would be useful to accept a dict key "custom" that contains random data in dictionary format, that can be used by customer specific tools, in my case, a device can have a unique identifier in CMDB that I want to include in the metadata, or a particular role or feature that is. It part of the config and is specific to my organization.

Which component of AVD is impacted

eos_cli_config_gen

Use case example

Customer specific device level metadata

Describe the solution you would like

An additional key in the metadata schema that accepts any dictionary structure of random keys.

Describe alternatives you have considered

None

Additional context

No response

Contributing Guide

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[ClausHolbechArista]

All schemas support custom keys starting with underscore.