feat(webhooks & callbacks): add contracts for webhooks and callbacks

[sufyankhanrao]

What

• Added verifier interface for custom signature verification.
• Introduced a framework-agnostic request model.
• Added verification result model for standardized success/failure handling.

Why

To provide stable, language-agnostic contracts enabling consistent webhook and callback implementations across core libraries and SDKs.

Closes #36

Type of change

Select multiple if applicable.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause a breaking change)
• Tests (adds or updates tests)
• Documentation (adds or updates documentation)
• Refactor (style improvements, performance improvements, code refactoring)
• Revert (reverts a commit)
• CI/Build (adds or updates a script, change in external dependencies)

Dependency Change

If a new dependency is being added, please ensure that it adheres to the following guideline https://github.com/apimatic/apimatic-codegen/wiki/Policy-of-adding-new-dependencies-in-the-core-libraries

Breaking change

If the PR is introducing a breaking change, please ensure that it adheres to the following guideline https://github.com/apimatic/apimatic-codegen/wiki/Guidelines-for-maintaining-core-libraries

Testing

List the steps that were taken to test the changes

Checklist

• My code follows the coding conventions
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added new unit tests

[Copilot]

Pull Request Overview

This pull request adds comprehensive contracts for webhook and callback handling by introducing a signature verification framework and HTTP request modeling. The changes enable language-agnostic webhook implementations across core libraries and SDKs.

• Added signature verification interface with standardized result handling
• Introduced framework-agnostic HTTP request model for webhook processing
• Updated package structure and documentation to reflect new capabilities

Reviewed Changes

Copilot reviewed 8 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
setup.py	Version bump from 0.1.6 to 0.1.7
apimatic_core_interfaces/security/verification_result.py	New model for standardized verification outcomes
apimatic_core_interfaces/security/signature_verifier.py	Abstract interface for signature verification implementations
apimatic_core_interfaces/security/init.py	Package initialization for security module
apimatic_core_interfaces/http/request.py	Framework-agnostic HTTP request model
apimatic_core_interfaces/http/init.py	Package initialization for HTTP module
apimatic_core_interfaces/init.py	Updated main package exports
README.md	Documentation updates with new interfaces and models

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[sonarqubecloud]

Quality Gate failed

Failed conditions
0.0% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud