TPT-4278: python-sdk: Implement support for Reserved IP for IPv4

[mgwoj]

📝 Description

Add full Reserved IP support to the Python SDK (linode_api4-python). Currently there is no reserved IP support in the SDK. This story covers new object classes, networking group methods, and updates to existing objects.

✔️ How to Test

make test-unit

[Copilot]

Pull request overview

Adds Reserved IPv4 (Reserved IP) support across the SDK, including new networking objects, networking group endpoints, and integration with existing tagging and allocation flows.

Changes:

• Introduces Reserved IP models (ReservedIPAddress, ReservedIPType, ReservedIPAssignedEntity) and exposes reserved/tags/assigned_entity on IPAddress.
• Adds networking group methods for listing/creating reserved IPs and fetching reserved IP types/pricing.
• Extends tagging and allocation APIs/tests to support reserved IPv4 assignment (Instance/NodeBalancer/Tag flows), plus new fixtures and pytest config.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
test/unit/objects/tag_test.py	Adds unit coverage for tagged reserved IPv4 objects and tag creation with reserved IPv4s.
test/unit/objects/networking_test.py	Adds unit coverage for Reserved IP fields, save/delete flows, and Instance IP allocation with explicit address.
test/unit/groups/networking_test.py	Adds unit coverage for networking group reserved IP list/create/types and reserved-vs-ephemeral allocation behavior.
test/fixtures/networking_reserved_ips.json	Fixture data for listing reserved IPs.
test/fixtures/networking_reserved_ips_types.json	Fixture data for reserved IP type pricing.
pytest.ini	Adds pytest discovery defaults and marker declarations.
conftest.py	Ensures repo root is importable for pytest runs from arbitrary working dirs.
linode_api4/objects/tag.py	Enables tagged object resolution for reserved_ipv4_address and supports non-id identifiers via id_attribute.
linode_api4/objects/networking.py	Adds Reserved IP object models and new/updated IP-related properties.
linode_api4/objects/linode.py	Extends Instance.ip_allocate to optionally assign a reserved IPv4 address.
linode_api4/groups/tag.py	Adds reserved_ipv4_addresses support to tag creation.
linode_api4/groups/nodebalancer.py	Adds optional ipv4 param to assign a reserved IPv4 at NodeBalancer creation.
linode_api4/groups/networking.py	Extends ip_allocate for reserved IP allocation and adds reserved IP list/create/types group methods.
linode_api4/groups/linode.py	Adds ipv4 parameter for assigning reserved IPv4s at instance creation.

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[Copilot]

ip_allocate's docstring describes required arguments (linode required when reserved=False; region or linode required when reserved=True), but the implementation never validates these combinations. This allows requests to be sent without linode_id/region (or with region while reserved is False), which will fail at the API with a less actionable error. Add explicit argument validation (raise ValueError) to enforce the documented contract before building/sending the request body.

[Copilot]

entities uses a mutable default ([]). Even though this method currently only iterates it, mutable defaults are easy to misuse later and are discouraged because they can create cross-call shared state if mutated. Prefer entities=None and then set entities = entities or [] inside the function.