Incorrect Handling of securityDefinitions for OpenAPI 3 in _builders.py

[mateus-sj]

Issue: Incorrect Handling of securityDefinitions for OpenAPI 3 in _builders.py

Description:

I've identified an issue in the OpenApiDocBuilder class where the handling of securityDefinitions for OpenAPI 3 is not consistent with the OpenAPI 3 specification. For more details, refer to the Authentication and Authorization official documentation from Swagger.

Usage

security_definitions = {
        "Bearer": {
            "type": "apiKey",
            "name": "Authorization",
            "in": "header",
            "description": "Enter your Bearer token in the format: Bearer <token>"
        }
    }
security = [{"Bearer": []}]
setup_swagger(url_specs,
              swagger_url="/api/docs",
              api_version="1.0",
              title="My API Title",
              description="My API description",
              schemes=["http", "https"],
              security_definitions=security_definitions,
              security=security,
              api_definition_version="openapi-3"
              )

Current Behavior:

The "Authorize" option does not appear at the Swagger UI. The code for _builders.py (line 256) currently sets the securityDefinitions directly under the main Swagger spec:

if security_definitions:
    swagger_spec["securityDefinitions"] = security_definitions

Expected Behavior:

According to the OpenAPI 3 specification, the securityDefinitions should be nested inside the components section under the key securitySchemes.

The correct implementation should look like this:

if security_definitions:
    swagger_spec["components"]["securitySchemes"] = security_definitions

After the proposed changes i was able to use the "Authorization" button in the Swagger UI and it works properly.

Thank you for the awesome repo!