fix: check duplicates schemas when loading swagger

[Marwen94]

Closes #156

[codecov]

Codecov Report

Merging #157 (45dd535) into master (a29b4f9) will increase coverage by 0.12%.
The diff coverage is 100.00%.

@@ Coverage Diff @@ ## master #157 +/- ## ========================================== + Coverage 95.97% 96.09% +0.12%  ========================================== Files 18 18 Lines 547 564 +17 Branches 103 109 +6 ========================================== + Hits 525 542 +17  Misses 12 12 Partials 10 10 

Impacted Files	Coverage Δ
openapi_spec_validator/handlers/compat.py	90.90% <100.00%> (+30.90%)	⬆️
openapi_spec_validator/handlers/file.py	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update a29b4f9...45dd535. Read the comment docs.

[Marwen94]

@p1c2u could you please have a look at this PR ?

[p1c2u]

Looks good. Just wondering how this affects the performance.

[Marwen94]

Looks good. Just wondering how this affects the performance.

I don't think this influences a lot the performance since it only adds an o(n) complexity where n is the number of schema in a given swagger. Imho n in a real world context is in [1, 100].

We can set the duplicate check optional also, what do you think ?