feat: Add support for Bearer token (access token) authentication

[egorpavlikhin]

Summary

• Adds support for short-lived access tokens (Bearer tokens) as an alternative to API key authentication
• New CLI option --access-token / -t and environment variable OCTOPUS_ACCESS_TOKEN
• Access token takes precedence when both credentials are provided
• The @octopusdeploy/api-client SDK already supports this via the accessToken property on ClientConfiguration

Note: Bearer token auth is intended only for automated scenarios (CI/CD pipelines, orchestration, machine-to-machine workflows) where the issued token is short-lived.

Files changed

• src/helpers/getClientConfigurationFromEnvironment.ts — Core auth logic supporting both credential types
• src/index.ts — New --access-token CLI option
• src/helpers/errorHandling.ts — Updated auth error messages
• src/tools/__tests__/testSetup.ts — Test config supports access tokens
• README.md — New Authentication section documenting both methods
• .env.example — Documents OCTOPUS_ACCESS_TOKEN

Test plan

• npm run build compiles cleanly
• Start server with --access-token flag and verify it connects
• Set OCTOPUS_ACCESS_TOKEN env var and verify it connects
• Provide neither API key nor access token — verify clear error message
• Provide both — verify access token is used

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