Function caseWhen

caseWhen(): CaseBuilder
Start a "searched" CASE expression: CASE WHEN cond1 THEN result1 [WHEN cond2 THEN result2 ...] [ELSE else] END

Returns CaseBuilder
Example
```
caseWhen()
  .when({ age: { [Op.gte]: 18 } }, 'adult')
  .else('minor')
  .as('ageGroup')
```
- Defined in query-builders/functions/conditional.ts:581