feat: set flag `readonly` recursively

[MatteoVoges]

Motivation

I want a function that sets a value for a flag (atm readonly, but can be extended for all / generic flags) recursively.

Have you read the Contributing Guidelines on pull requests?

Yes.

Test Plan

Tests will be added if the basic structure is confirmed.

Fixes

Fixes #1123

[MatteoVoges]

@odelalleau with this I get:

from omegaconf import OmegaConf

config = OmegaConf.create({"a": {"b": 1}})

OmegaConf.set_readonly(config.a, True)
OmegaConf.set_readonly_recursively(config, False)
print(OmegaConf.is_readonly(config.a))
# >>> False

[odelalleau]

Thanks! I would suggest to do it a bit differently to have a more generic implementation:

• Add a recursive boolean argument to _set_flag()
• Also add it to set_struct() and set_readonly() (instead of adding a different function specific to readonly)

[odelalleau]

Thanks for the update -- overall looks good to me, but I won't have time to look at it in details until next week. We'll need to add a news fragment as well and update the documentation.

[indigoviolet]

@omry @odelalleau this is a blocker for #1102, would be great to get it in