Consolidate the various approaches for making custom calls to the Genesys Cloud API apart from the SDK Client into a single Custom API Client library.

[bbbco]

Introduces a shared custom_api_client package that wraps the SDK's APIClient.CallAPI() method, then migrates all proxy files that were making direct CallAPI or raw http.Client calls to
use it. This eliminates ~1,400 lines of duplicated boilerplate (authorization headers, content-type negotiation, query parameter encoding, error handling, JSON unmarshaling) across 21
files.

Motivation

Proxy files that needed to call API endpoints without generated SDK methods were each independently constructing HTTP requests — building auth headers, setting content types, encoding query params, handling errors, and unmarshaling responses. This was error-prone, inconsistent, and created a maintenance burden. Some files used APIClient.CallAPI() directly, others used raw net/http.Client, and each had slightly different error handling.

What's included

New package: genesyscloud/custom_api_client/

• Client struct with callAPIAttr function attribute (same pattern as proxy files for testability)
• Do[T] — generic typed JSON response
• DoNoResponse — for DELETE / PUT with no return body
• DoRaw — raw []byte response for custom unmarshaling
• DoWithAcceptHeader — custom Accept header (e.g., text/csv)
• QueryParams type alias (url.Values) + NewQueryParams() helper
• Method constants (MethodGet, MethodPost, MethodPut, MethodPatch, MethodDelete)
• 19 unit tests using mocked function attribute injection

Migrated files (21 files across 16 packages):

Package	Files	Pattern replaced
process_automation_trigger	proxy + data source	CallAPI ×4, pagination fixed to relative paths
architect_datatable	proxy	CallAPI ×2
architect_datatable_row	proxy	CallAPI ×1
integration_action	proxy	CallAPI ×4 (upload function untouched)
scripts	proxy	CallAPI ×1 + http.Client ×1
guide	proxy + utils	http.Client (6 helper functions deleted)
guide_version	proxy + utils	http.Client (utils file deleted)
recording_media_retention_policy	proxy	CallAPI ×1
knowledge_document	proxy	CallAPI ×1
telephony_providers_edges_trunkbasesettings	proxy	CallAPI ×1
business_rules_schema	proxy	CallAPI ×1
task_management_workitem_schema	proxy	CallAPI ×1
task_management_worktype_status_transition	proxy	CallAPI ×1
external_user	proxy	CallAPI ×1
architect_flow	proxy	http.Client (makeFlowRequest deleted)
user	utils	CallAPI ×2 (buildHeaderParams deleted)
routing_queue	members	CallAPI ×1

Documentation:

• Package-level Go doc with usage examples, when to use / not use, query param patterns
• New "Custom API Client" section added to README.md under developer guidance

What was NOT changed

• S3 upload logic (scripts, architect_grammar_language, architect_user_prompt, responsemanagement_responseasset)
• Integration action upload function (presigned URL flow)
• Schema, CRUD, or test files
• Proxy function attribute signatures (only internal implementations changed)
• Any proxy already using SDK methods properly