Fix/workflow validation ~10 delegation monitor limit

[thecodingshrimp]

Description

This PR fixes a bug in workflow validation where creating a Security Analytics detector with more than 10 rules fails with an "invalid monitor ids" error (#2144).

Root Cause:
The validateMonitorAccess() function in TransportIndexWorkflowAction.kt was not setting an explicit size parameter on the search query. This caused OpenSearch to default to returning only the first 10 results. When a Security Analytics detector referenced more than 10 rules (generating more than 10 delegate monitors), the validation would incorrectly report that the additional monitor IDs were invalid.

The Fix:
Added .size(monitorIds.size) to the SearchSourceBuilder on line 716 to ensure all delegate monitor IDs are returned and validated correctly.

Code Change:

// Before
val searchSource = SearchSourceBuilder().query(query)

// After
val searchSource = SearchSourceBuilder().query(query).size(monitorIds.size)

Impact:

• Fixes detector creation for rule sets with more than 10 rules
• Eliminates misleading "invalid monitor ids" error messages
• Ensures workflow validation correctly handles workflows of any size (up to the existing 25 delegate limit)

Related Issues

#2144

Example Error (Before Fix):

Error 400 (Bad Request): 0uhbOp4BCrnc_R8wysGB, 1-hbOp4BCrnc_R8wysGD, 2uhbOp4BCrnc_R8wysGG are not valid monitor ids [type=security_analytics_exception]

Check List

• New functionality includes testing.
  • Not applicable: This is a bug fix for existing functionality. The existing test suite in WorkflowRestApiIT.kt validates workflow creation and monitor validation scenarios.
• New functionality has been documented.
  • Not applicable: This is a bug fix, not new functionality.
• API changes companion pull request created.
  • Not applicable: No API changes.
• Commits are signed per the DCO using --signoff.
• Public documentation issue/PR created.

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