attributionConfidence property
The confidence of the returned attribution. Possible string values are:
- "UNKNOWN_ATTRIBUTION_CONFIDENCE" : Unset.
 - "WEAK" : Weak confidence, more than one matching link found or link suspected to be false positive.
 - "DEFAULT" : Default confidence, match based on device heuristics.
 - "UNIQUE" : Unique confidence, match based on "unique match link to check" or other means.
 
Implementation
core.String? attributionConfidence;