feat(AWS Lambda): Support advanced logging configuration

[jimmyn]

Summary

Implements AWS Lambda advanced logging configuration support as requested in serverless/serverless#12264. This feature enables developers to configure JSON-formatted logs, application log levels, system log levels, and custom log groups for Lambda functions at both provider and function levels.

Related to serverless/serverless#12315 (originally targeting v3 branch).

Based on AWS announcement: https://aws.amazon.com/blogs/compute/introducing-advanced-logging-controls-for-aws-lambda-functions/

Implementation

• Schema validation (lib/plugins/aws/provider.js):

  • Added provider.logs.lambda configuration with validation for:
    • applicationLogLevel: DEBUG, ERROR, FATAL, INFO, TRACE, WARN
    • logFormat: JSON, Text
    • logGroup: Custom log group path (1-512 characters)
    • systemLogLevel: DEBUG, INFO, WARN
  • Added function-level logs property with same schema
  • Function-level configuration overrides provider-level configuration

• CloudFormation compilation (lib/plugins/aws/package/compile/functions.js):

  • Implements inheritance: function logs override provider.logs.lambda
  • Converts YAML logs config to CloudFormation LoggingConfig property with proper PascalCase mapping

• Documentation:

  • Updated functions.md with provider and function-level examples
  • Updated serverless.yml.md with provider.logs.lambda configuration
  • Shows inheritance behavior clearly

• Comprehensive testing (373 lines total):

  • Tests for all valid/invalid values at function level
  • Tests for provider-level configuration
  • Tests for function-level overriding provider-level
  • CloudFormation output verification

Configuration Examples

Provider-level (applies to all functions):

provider:
  logs:
    lambda:
      logFormat: JSON
      applicationLogLevel: INFO
      systemLogLevel: WARN
      logGroup: /aws/lambda/global-log-group

Function-level (overrides provider):

functions:
  hello:
    handler: handler.handler
    logs:
      applicationLogLevel: DEBUG
      logFormat: JSON
      logGroup: /aws/lambda/custom-log-group
      systemLogLevel: DEBUG

Test Plan

• Schema validation tests for all applicationLogLevel values (DEBUG, ERROR, FATAL, INFO, TRACE, WARN)
• Schema validation tests for all logFormat values (JSON, Text)
• Schema validation tests for all systemLogLevel values (DEBUG, INFO, WARN)
• Invalid value rejection tests
• Provider-level logs.lambda configuration test
• Function-level overrides provider-level test
• CloudFormation LoggingConfig property generation
• Integration with existing function compilation
• All 23 logging-related tests passing

Closes serverless/serverless#12264
Related: serverless/serverless#12315

[mnapoli]

Thanks!