Purge CDN cache by ARL [RHELDST-17152]

[rbikar]

This change adds functionality for purging CDN cache by ARLs.

• arguments required for purging CDN cache can be passed via environment variables.
• publishing repositories and purging CDN cache was refactored and encapsulated to Publisher class in order to have cleaner code
• TTL required for ARL generation is requested from CDN service. If live data are not available, we fall back to default values.

[rbikar]

run tests

[codecov[bot]]

Codecov Report

Patch coverage: 98.83% and project coverage change: +0.28 :tada:

Comparison is base (f65ddbb) 96.58% compared to head (82d01f4) 96.86%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #204 +/- ## ========================================== + Coverage 96.58% 96.86% +0.28% ========================================== Files 7 8 +1 Lines 850 990 +140 ========================================== + Hits 821 959 +138 - Misses 29 31 +2 ``` | [Impacted Files](https://app.codecov.io/gh/release-engineering/ubi-population-tool/pull/204?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=release-engineering) | Coverage Δ | | |---|---|---| | [ubipop/\_cdn.py](https://app.codecov.io/gh/release-engineering/ubi-population-tool/pull/204?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=release-engineering#diff-dWJpcG9wL19jZG4ucHk=) | `98.73% <98.73%> (ø)` | | | [ubipop/\_\_init\_\_.py](https://app.codecov.io/gh/release-engineering/ubi-population-tool/pull/204?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=release-engineering#diff-dWJpcG9wL19faW5pdF9fLnB5) | `93.85% <100.00%> (-0.30%)` | :arrow_down: |

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[rbikar]

run tests

[rbikar]

run tests

[rbikar]

integration tests env seems to be broken, filed RHELDST-17867

[rbikar]

It looks that this got a bit lost, @rohanpm @jm-wk can you have a look, please? Thx.

[rbikar]

rebased - merging