feature: Added get endpoints for Interface tag ranges

[Alopalao]

Closes #162

Summary

This is based on the branch epic/vlan_pool which is not going to be modified.
Added endpoints:

• GET v3/interfaces/{interface_id}/tag_ranges
• GET v3/interfaces/tag_ranges

Local Tests

Called these new API endpoints
Added unit tests

End-to-End Tests

N/A

Note:
Tox is passing

[viniarck]

Functionality-wise looks good. Asked a few changes to avoid thread-safety issues. Also, don't forget to update the changelog.

I'll also recommend that now that you have this endpoint to add a new e2e test covering it, I believe a least one e2e covering these points below should be great, feel free to add other ones as you wish:

Here's a suggestion for one e2e test case step (feel free to adapt or change accordingly):

• Restrict tag ranges on a UNI interface on a ring topology
• Try to create an EVC, confirm that it won't allow it
• Confirm that both tag ranges endpoints are returning the expected responses
• Add another tag range restriction that's compatible with the UNI vlan that you want to use, now the EVC should be created successfully
• Remove the tag ranges restriction confirm the expected responses

This is a larger test to cover a more elaborated scenario, but feel free to create smaller ones to test individually, it's up to you, thanks, Aldo.

[viniarck]

Nicely done @Alopalao.

I'll wait for the new e2e test(s) before approving for completeness.

[viniarck]

Excellent PR, Aldo. Awesome how the endpoints turned out.

I'll leave it pre-approved. Feel free to merge it once Italo also approves mef_eline PR kytos-ng/mef_eline#371 when he returns to the office.