Fix: unable to parse OpenAPI spec

[sternakt]

Description

Fixes #301

Type of change

• Documentation (typos, code examples, or any documentation updates)
• Bug fix (a non-breaking change that resolves an issue)
• New feature (a non-breaking change that adds functionality)
• Breaking change (a fix or feature that would disrupt existing functionality)
• This change requires a documentation update

Checklist

• I have conducted a self-review of my own code
• I have made the necessary changes to the documentation
• My changes do not generate any new warnings
• I have added tests to validate the effectiveness of my fix or the functionality of my new feature
• I have included code examples to illustrate the modifications

[codecov]

Codecov Report

Attention: Patch coverage is 82.85714% with 6 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
fastagency/api/openapi/security.py	86.95%	2 Missing and 1 partial ⚠️
fastagency/api/openapi/security_schema_visitor.py	50.00%	1 Missing and 1 partial ⚠️
fastagency/api/openapi/client.py	50.00%	0 Missing and 1 partial ⚠️

Files with missing lines	Coverage Δ
fastagency/helpers.py	94.28% <100.00%> (+1.18%)	⬆️
fastagency/api/openapi/client.py	85.61% <50.00%> (-0.11%)	⬇️
fastagency/api/openapi/security_schema_visitor.py	80.00% <50.00%> (+2.22%)	⬆️
fastagency/api/openapi/security.py	84.26% <86.95%> (+1.91%)	⬆️

... and 1 file with indirect coverage changes