Handle settings drift for all resources

[deanhuynh]

Adds a new mergeSettings helper to better identify drift across relevant resources (sources, destinations, destination_subscriptions, warehouses, profile_warehouses, and insert_functions). This helper now diffs settings present in the config with their actual backend values except if they are censored or the password field for warehouses which have special handling as their returned API values are different than the backend values.

Tested each resource along with relevant diffs.

Addresses #200

[Copilot]

Pull Request Overview

This PR introduces a new mergeSettings helper function to improve settings drift detection across Terraform resources. The main goal is to properly handle the difference between config-defined settings and backend-generated settings by merging only the relevant values.

Key changes:

• Added a new mergeSettings utility function that preserves config-defined keys while detecting drift from backend values
• Updated 6 resource types (sources, destinations, destination_subscriptions, warehouses, profile_warehouses, insert_functions) to use this new merge logic
• Added special handling for warehouse password fields and censored secrets (indicated by bullet characters)

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
internal/provider/utils.go	Implements the core mergeSettings function with logic for handling censored secrets and warehouse passwords
internal/provider/utils_test.go	Comprehensive test suite for the mergeSettings function covering various scenarios
internal/provider/warehouse_resource.go	Updated to use mergeSettings with warehouse-specific handling
internal/provider/source_resource.go	Updated to use mergeSettings for drift detection
internal/provider/profiles_warehouse_resource.go	Updated to use mergeSettings with warehouse-specific handling
internal/provider/insert_function_instance_resource.go	Updated to use mergeSettings for drift detection
internal/provider/destination_subscription_resource.go	Updated to use mergeSettings for drift detection
internal/provider/destination_resource.go	Updated to use mergeSettings for drift detection
go.mod	Added testify dependency for test assertions

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