Add new pages to the examples covering the Auth procedure

[Kajetan-Narkiewicz-Planview]

- Add OAuth2 Authorization Code Flow example (py-oauth2-authorization-code/)
  - Complete flow with local callback server for OAuth redirect
  - Token refresh demonstration
  - Production-ready patterns with error handling

- Add OAuth2 Client Credentials Flow example (py-oauth2-client-credentials/)
  - Robot/service account authentication
  - Reusable OAuth2ClientCredentials class with automatic token management
  - Multiple authentication method examples (Basic Auth, body params)

- Add OAuth1 example (py-oauth1/)
  - Legacy authentication support
  - Complete 3-legged OAuth1 flow
  - Migration guidance to OAuth2

- Add AUTH_README.md with:
  - Decision guide for choosing authentication method
  - Quick comparison table
  - Security best practices
  - Troubleshooting guide

- Update main readme.md with authentication section and example index

Each example includes Python script, README with usage instructions,
and requirements.txt for dependencies.

[Copilot]

Pull request overview

Adds new authentication-focused example pages/scripts to the examples/ area to help developers choose and implement the right ProjectPlace auth flow (OAuth2 Auth Code, OAuth2 Client Credentials, and legacy OAuth1), plus updates the examples index/docs to highlight them.

Changes:

• Adds new Python example directories for OAuth2 Authorization Code, OAuth2 Client Credentials, and OAuth1 flows (each with script, README, requirements).
• Adds examples/AUTH_README.md as an authentication decision guide and updates examples/readme.md to index auth examples.
• Adds an examples/.gitignore for common local Python artifacts and credential files.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 11 comments.

Show a summary per file

File	Description
examples/readme.md	Adds an authentication “getting started” section and indexes auth examples.
examples/AUTH_README.md	Adds an auth method decision guide, comparison table, and best practices.
examples/.gitignore	Adds ignore patterns for venvs, IDE files, and local credential files.
examples/py-oauth2-authorization-code/requirements.txt	Adds Python dependency list for the auth-code example.
examples/py-oauth2-authorization-code/readme.md	Documents the OAuth2 auth-code example usage and concepts.
examples/py-oauth2-authorization-code/oauth2_authorization_code.py	Implements an interactive local-callback OAuth2 auth-code flow demo.
examples/py-oauth2-client-credentials/requirements.txt	Adds Python dependency list for the client-credentials example.
examples/py-oauth2-client-credentials/readme.md	Documents the OAuth2 client-credentials example usage and concepts.
examples/py-oauth2-client-credentials/oauth2_client_credentials.py	Implements client-credentials flow plus a reusable helper class.
examples/py-oauth1/requirements.txt	Adds Python dependencies for the OAuth1 example.
examples/py-oauth1/readme.md	Documents the legacy OAuth1 example and migration guidance.
examples/py-oauth1/oauth1_flow.py	Implements a 3-legged OAuth1 flow demo.

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