Feat(utils): psql unique index instead of constraint (#6386)

**What**
- always return an index expression, also for unique constraints

**why**
- constraints can't be partial, meaning `UNIQUE ... WHERE` is not possible with constraints
- constraints are indicies under the hood so it doesn't change the behavior of the system when we're not using constraint specific features but just using them for `UNIQUE`

packages/utils/src/common/__tests__/create-psql-index-helper.ts

@@ -73,9 +73,9 @@ describe("createPsqlIndexStatementHelper", function () {
 
     const indexStatement = createPsqlIndexStatementHelper(options)
     expect(indexStatement).toEqual(
-      `ALTER TABLE IF EXISTS "${options.tableName}" ADD CONSTRAINT "${
-        options.name
-      }" UNIQUE (${options.columns.join(", ")}) WHERE ${options.where}`
+      `CREATE UNIQUE INDEX IF NOT EXISTS "${options.name}" ON "${
+        options.tableName
+      }" (${options.columns.join(", ")}) WHERE ${options.where}`
     )
   })
 })