[jmgasper]

The latest PM-6672 comment asks for a single dimension selector that displays all categories together in the monthly chart and table.

• Add groupBy=offeringType|dealCategory|customerType for bookings, pipeline and revenue, plus stage for pipeline.
• Return complete category series for won bookings, open pipeline Amount / Expected Amount, and revenue. Preserve won/open separation, fiscal dates, expected-value fallback and full customer totals. Legacy requests without groupBy retain their existing responses.
• Keep every category visible, including Unknown values, and combine legacy customer-type spellings into the canonical category. Report missing dimensions explicitly without substituting an ungrouped total.
• Document the new parameter and the matching UI's one-selector behavior. No database migration or Salesforce report-definition changes.

Validation: lint and build pass on both target branches; 116 affected dashboard and Sales tests pass on each. Coverage includes every dimension, both date bases, expected weighting, all revenue categories, customer totals, invalid combinations and missing source fields.

Deploy this API before the companion platform-ui changes.

Jira comment: https://topcoder.atlassian.net/browse/PM-6672?focusedCommentId=139914

Companion UI: topcoder-platform/platform-ui#2573