[DTC] Client changes to set Weight as an Optional field for Policy

[Tejashree-RS]

Summary

Sets weight as an optional field on the PolicyPool model to align with the upstream API schema, where weight is not required when associating a pool to a DTC policy.

Type of Change

• 🆕 New API / Model
• 🔧 Update Existing Schema or Model
• 🐛 Bug Fix
• 📝 Documentation
• 🧹 Maintenance (dependency upgrades, CI, refactoring)

Affected Packages

• anycast
• cloud_discovery
• dfp
• dns_config
• dns_data
• dtc
• fw
• infra_mgmt
• infra_provision
• ipam
• ipam_federation
• keys
• redirect
• upgrade_policy
• universal_ddi_client

Resource / Model: PolicyPool
Description: Changed weight on PolicyPool from required to optional (default None).

Schema Changes

• New model added
• New field(s) added to existing model
• Field(s) removed or renamed
• Required fields changed

Detailed Changes (click to expand)

File	Change
src/dtc/models/policy_pool.py	Changed weight field to Optional[int] = None
src/dtc/docs/PolicyPool.md	Updated weight field documentation to mark as optional

Ticket / Issue

Fixes #

Changelog Inclusion

• Consider for changelog and release notes addition

Additional Context

Without this fix, creating a PolicyPool without explicitly specifying a weight would raise a validation error, even though the upstream API treats it as optional.