docs: API & Event stream documentation and format changes #5798 #5801

[gayanath8]

Issue Labels

#5798
#5801

Requirements

• Audit all existing Guardian API endpoints and identify documentation gaps.
• Improve documentation for every existing API endpoint, including: endpoint URL, HTTP method, authentication requirements, request payload schema with field descriptions, response payload schema, and error codes.
• Add documentation for any API endpoints that are currently undocumented.
• Generalize and clearly document each supported API block's execution payload structure.
• Keep provisions in the documentation for dynamic fields defined by users within policies.
• Provide example request/response pairs for common workflows.
• Update the Application Events Module documentation page with comprehensive, current information about all available event types, their payloads, and usage patterns.
• Fill in the External Events documentation page with all current event types supported by Guardian's event stream.
• Each event type should be documented with: event name, trigger condition, payload structure, and example usage.
• Include guidance on how external systems should subscribe to and consume these events.

Summary of Changes

• Added documentation for previously undocumented API endpoints
• Introduced the Policy Block API Execution Payloads guide
• Reformatted all existing API documentation
• Filled documentation gaps and restructured event stream docs
• Corrected and expanded the execution payloads guide with source-verified block entries
• Updated SUMMARY.md to reflect the reorganized structure.