Search ext: Aggregate field fixes

[colemanw]

Overview

Fixes a search extension regression in 5.30 where field labels failed to display in the "Aggregate Fields" section.
Also fixes common crashes caused by MYSQL's only-full-group-by mode, by assigning a default aggregator to non-grouped fields.
Also fixes a bug where aggregating a field would fail to update the ORDER BY clause.

Before

After

Comments

Targets 5.30 branch since it addresses a regression in 5.30, and this is still a very new extension.

[civibot]

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[eileenmcnaughton]

ok without test as angular layer only

[eileenmcnaughton]

It works! I added the before & after images to the PR template

[eileenmcnaughton]

@colemanw this fixes the problem as described (& so these comments can be for a follow up PR) but I tested to try to

• get totals of line items grouped by financial type id

Screenshot below but I note

1. I think we should use group_concat distinct for list rather than group_concat (we might have an option but for default I think distinct is better)
2. why hasn't it displayed the financial type name?

[eileenmcnaughton]

Also - the Nan thing.... when you add a $ field to already-displayed-results