RUBY-3667 BSON::ObjectId(object_id) returns its argument when it is already an ObjectId

[jamis]

When given an existing ObjectId, BSON::ObjectId(object_id) should simply return its argument, rather than converting it to a string and reparsing it.

Thank you to @johnnyshields for the implementation.

[Copilot]

Pull request overview

Updates the BSON::ObjectId(...) convenience constructor to avoid unnecessary string conversion + re-parsing when the argument is already a BSON::ObjectId, preserving object identity and reducing overhead.

Changes:

• Make BSON::ObjectId(object_id) return object_id directly when it is already a BSON::ObjectId.
• Update YARD documentation for BSON::ObjectId(...) to describe the expanded accepted input type.
• Extend the top-level BSON spec to assert identity preservation for existing BSON::ObjectId inputs.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
spec/bson_spec.rb	Adds coverage that BSON::ObjectId(existing_object_id) returns the same instance, and scopes the existing string case into its own context.
lib/bson.rb	Implements early return for BSON::ObjectId arguments and updates method documentation accordingly.

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