Add ignore_resource_types to drift command

[cmc-ron]

Context

AWS CloudFormation drift detection does not support all resource types. Resources like AWS::ElastiCache::ParameterGroup and AWS::ElastiCache::SubnetGroup return UNKNOWN drift status, causing stack_master drift to exit 1 even when all supported resources are in sync. This triggers false-positive CI failures in drift detection pipelines daily.

Problem

No mechanism exists to exclude specific resource types from drift failure evaluation.

Solution

Add an optional ignore_resource_types key to the stack definition. When set, resources whose resource_type matches an entry in the list are excluded before evaluating whether to call failed. All resources are still displayed for visibility — only the failure gate is affected.

Example stack_master.yml:

market-redis-blue:
  template: redis-replication-group.yml.erb
  ignore_resource_types:
    - AWS::ElastiCache::ParameterGroup
    - AWS::ElastiCache::SubnetGroup

Checklist

• Existing tests pass
• New spec covers ignore_resource_types filtering
• Behaviour is unchanged when ignore_resource_types is not set

🤖 Generated with Claude Code