[FEATURE REQUEST] Support for deleting unconfigured lines in file.keyvalue

[tacerus]

Is your feature request related to a problem? Please describe.

Currently the file.keyvalue state function only allows for either the modification of existing lines, or the addition of new lines.
It would be great if it could be used to prune lines not passed to be configured.

Describe the solution you'd like

Add an optional argument, such as clean, which, if set to true, enables the deletion of lines not passed via key_values: {}.

Describe alternatives you've considered

• Use additional states with dependency logic to prune the file before executing file.keyvalue.

• Use file.managed and construct the key value pairs manually .

Additional context

I will submit a proposed patch.

Please Note
If this feature request would be considered a substantial change or addition, this should go through a SEP process here https://github.com/saltstack/salt-enhancement-proposals, instead of a feature request.

[OrangeDog]

This is what file.serialize does when using the keyvalue serializer without the merge_if_exists option.