CRED-2151: Add PAT auth support to Ruby API client

[tausman]

Why

Adds Personal Access Token (PAT) auth support to the Ruby API client. PATs authenticate via the Authorization: Bearer <PAT> header. The OpenAPI spec now defines bearerAuth as a proper security scheme with x-env-name: DD_BEARER_TOKEN, so this change enables the generator to handle it automatically.

Behavior

When DD_BEARER_TOKEN is set (or config.access_token is set programmatically), the Authorization: Bearer <token> header is sent alongside any configured API key and app key headers. Auth methods are not mutually exclusive — all configured headers are sent, and the server uses whichever is valid.

• DD_BEARER_TOKEN set → sends Authorization: Bearer <token>
• DD_API_KEY set → sends DD-API-KEY header
• DD_APP_KEY set → sends DD-APPLICATION-KEY header
• All three can be sent simultaneously

Summary

Generator templates (.generator/src/generator/templates/):

• configuration.j2: Uncommented the bearerAuth block so bearer auth is auto-generated from the OpenAPI spec. Added env var loading for http/bearer type security schemes (picks up DD_BEARER_TOKEN from x-env-name).
• api_client.j2: Added nil/empty value guard to skip auth settings with no configured value. Added Authorization to redacted headers in debug output.

Generated files (matching template output):

• lib/datadog_api_client/configuration.rb: bearerAuth entry in auth_settings using the existing access_token attribute. Loads DD_BEARER_TOKEN env var into @access_token.
• lib/datadog_api_client/api_client.rb: Skips auth entries with nil/empty values. Redacts Authorization header in debug logs.

Tests:

• spec/api_client_spec.rb: Tests that all configured auth headers are sent simultaneously. Tests bearer-only and API+app-key-only scenarios. Tests Authorization header redaction.
• spec/configuration_spec.rb: Tests access_token defaults, direct setting, DD_BEARER_TOKEN env var loading, and bearerAuth auth_settings entries.

Test plan

• Unit tests pass (35 examples, 0 failures)
• Live verification against staging (api.datad0g.com): Bearer auth returns HTTP 200
• No secrets/credentials in committed files
• Env var is DD_BEARER_TOKEN matching OpenAPI spec x-env-name

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PR Stack

API Client Libraries

• Go: CRED-2147: Add PAT auth support to Go API client datadog-api-client-go#3764 — CRED-2147: Add PAT auth support to Go API client
• Python: CRED-2146: Add PAT auth support to Python API client datadog-api-client-python#3243 — CRED-2146: Add PAT auth support to Python API client
• TypeScript: CRED-2148: Add PAT auth support to TypeScript API client datadog-api-client-typescript#3588 — CRED-2148: Add PAT auth support to TypeScript API client
• Java: CRED-2149: Add PAT auth support to Java API client datadog-api-client-java#3555 — CRED-2149: Add PAT auth support to Java API client
• Rust: CRED-2150: Add PAT auth support to Rust API client datadog-api-client-rust#1310 — CRED-2150: Add PAT auth support to Rust API client
• Ruby: CRED-2151: Add PAT auth support to Ruby API client #3058 — CRED-2151: Add PAT auth support to Ruby API client

OpenAPI Spec Changes

• https://github.com/DataDog/datadog-api-spec/pull/5166 — Add bearerAuth to global default security for PAT support
• https://github.com/DataDog/datadog-api-spec/pull/5164 — Add PAT/SAT management API endpoints (CRED-2275)