feat: add support for YAML file includes and nested includes in context

[dandonovsc]

🔧 Changes
Added YAML file include functionality to auth0-deploy-cli, allowing users to modularize their Auth0 configuration by splitting it into separate files and importing them using the !include directive.

New functionality:

Custom YAML type !include: Enables importing external YAML files within tenant configuration

resolveIncludes() function: Recursively processes YAML objects to resolve file includes with proper path resolution

Extended YAML schema: Modified the YAML context to support the new include syntax

Improved loadFile() method: Enhanced file path resolution with additional fallback mechanisms

# tenant.yaml
tenant:
  friendly_name: 'My Tenant'

clients: !include clients.yaml
roles: !include roles.yaml

This enables better organization of large Auth0 configurations by separating concerns into dedicated files while maintaining full compatibility with existing YAML functionality.

📚 References
This addresses the need for modular YAML configurations in auth0-deploy-cli, making it easier to manage complex Auth0 tenant setups by allowing configuration sections to be split across multiple files.

🔬 Testing
Automated tests added:

should process YAML with includes - Tests basic file inclusion functionality

should handle nested includes - Tests direct includes at root level

should error on missing include file - Tests error handling for missing files

Manual testing:

Create a main YAML file with !include directives

Create separate YAML files for each included section

Run a0deploy import -i tenant.yaml to verify includes are processed correctly

Verify that missing include files throw appropriate errors

Test coverage: All new functionality is covered by unit tests following existing patterns.

[kushalshit27]

Thank you for submitting this PR! Your contribution is greatly appreciated. We'll review it shortly

[kushalshit27]

Is it possible to use resolveIncludes before loadedYaml?

so that resolveIncludes can follow single responsibility.

[kushalshit27]

resolveIncludes recursively processes includes without cycle detection. If a YAML file directly or indirectly includes itself (e.g., a.yaml → b.yaml → a.yaml), this results in unbounded recursion and can crash the CLI with a stack overflow rather than surfacing a clear error.