Optionally allow extra keys in check-model-has-meta-keys

[fernandobrito]

Today check-model-has-meta-keys does not allow the model to have any other meta keys other than the ones required.

This PR introduces an optional argument to allow for it.
Our use case is that we need a check that checks that all models have, at a minimum, an "owner" meta key, while still allowing other meta keys (PII, etc).

The extra parameter has a False default value, meaning it is backward compatible with everyone that is using the check today.

More context on: #60

[codecov-commenter]

Codecov Report

Merging #65 (584fc80) into main (cc144b9) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main       #65   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           45        45           
  Lines         1956      1964    +8     
  Branches       258       259    +1     
=========================================
+ Hits          1956      1964    +8     

Impacted Files	Coverage Δ
pre_commit_dbt/check_model_has_meta_keys.py	100.00% <100.00%> (ø)

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[ssassi]

I think this is a nice feature. If you @BAntonellini fix conflicts and test this I'll merge it.