Returns aggregation buckets showing matching values and their record
counts. Use this BEFORE exact_search() to find the right value string.

Minimum 2 characters required for the search term.

GSA lists at most 100 values, most records first. When more values
match, truncated is true and other_records counts the records under
values not shown; use a longer term to narrow the list.

Example workflow:
1. suggest_contains('vendor_name', 'booz') -> finds 'Booz Allen Hamilton Inc.'
2. exact_search('vendor_name', 'Booz Allen Hamilton Inc.') -> all their rates