feat: add github_repository_custom_properties resource for batch property management

[mkushakov]

Resolves #3240

Summary

Add a new github_repository_custom_properties resource (plural) that manages multiple custom property values on a single repository in one resource block, with in-place updates when values change.

This complements the existing github_repository_custom_property resource (singular), which manages one property per resource instance and requires destroy+recreate on any change.

Motivation

The existing singular github_repository_custom_property resource has limitations:

• All fields are ForceNew — changing a property value destroys and recreates the resource, even though the GitHub API supports PATCH
• One resource per property — managing 10 properties on a repo requires 10 resource blocks
• Requires property_type — the user must manually specify the property type, even though it's already defined at the org level
• One API call per property — no batching

The new plural resource addresses all of these:

Capability	Singular (github_repository_custom_property)	Plural (github_repository_custom_properties)
Properties per resource	1	N
Value change behavior	Destroy + recreate	In-place update
Requires property_type	Yes	No (auto-detected from org definitions)
API calls	1 per property	1 for all properties (batch)
Import	owner/repo/property_name	owner/repo (imports ALL properties)

Changes

New Resource (resource_github_repository_custom_properties.go)

• Schema with repository_name (ForceNew) and property (TypeSet of name/value blocks)
• Create and Update share the same function — looks up org property definitions to auto-detect types, then calls CreateOrUpdateCustomProperties with all properties in a single API call
• Read filters to only managed properties (from state), or imports ALL properties when state is empty (import case)
• Delete sets all managed properties to nil in a single API call
• Custom StateContext importer that accepts owner/repo format and imports all properties
• Hash function based on property name only (not values), so value changes are detected as in-place modifications
• checkOrganization guard on all CRUD operations
• Proper error wrapping with fmt.Errorf and %w

Provider Registration (provider.go)

• Registered as github_repository_custom_properties

Tests (resource_github_repository_custom_properties_test.go)

• Creates and reads multiple properties — sets two properties (single_select + string) and verifies
• Updates property value in place — changes a single_select value from "production" to "staging" without destroy
• Imports all properties — creates properties, then imports via owner/repo
• Creates multi_select property — verifies multi-value property handling

All tests use providerFactories (modern pattern) and skipUnlessHasOrgs.

Example Usage

resource "github_repository_custom_properties" "example" {
  repository_name = github_repository.example.name

  property {
    name  = "environment"
    value = ["production"]
  }

  property {
    name  = "team"
    value = ["platform"]
  }

  property {
    name  = "languages"
    value = ["go", "typescript"]  # multi_select
  }
}

Relationship to Existing Resources

• github_repository_custom_property (singular) — unchanged, still available. Users can choose whichever pattern fits their workflow.
• github_organization_custom_properties — defines properties at the org level. The new resource reads these definitions to auto-detect property types.
• data.github_repository_custom_properties (data source) — already exists, reads all properties for a repo.

Note: Using both singular and plural resources on the same repository and property is not recommended, as they would conflict. Users should choose one pattern per repository.

Testing

• go build ./... — passes
• go vet ./... — passes

[github-actions]

👋 Hi! Thank you for this contribution! Just to let you know, our GitHub SDK team does a round of issue and PR reviews twice a week, every Monday and Friday! We have a process in place for prioritizing and responding to your input. Because you are a part of this community please feel free to comment, add to, or pick up any issues/PRs that are labeled with Status: Up for grabs. You & others like you are the reason all of this works! So thank you & happy coding! 🚀