Priority tiers for channel prioritization.

[Proto definition ![GitHub](https://developers.google.com/site-assets/logo-github.svg)](https://github.com/googleapis/googleapis/blob/master/google/ads/googleads/v26/enums/channel_priority_tier.proto)

| Enums ||
|---|---|
| ## `TIER1` | Primary priority tier (allocated first before lower tiers). |
| ## `TIER2` | Secondary priority tier (allocated remaining budget after Tier 1). |
| ## `UNKNOWN` | Used for return value only. Represents value unknown in this version. |
| ## `UNSPECIFIED` | Not specified. |