Generate Data Model does not emit primary_key: true for PostgreSQL tables with named PKs

Bug Description

When using Generate Data Model in Cube Playground (v1.6.23, PostgreSQL), primary key columns are not marked with primary_key: true in the generated YAML. This causes compile errors for any cube that has joins defined:

salesorderheader cube: primary key for 'salesorderheader' is required when join is defined
salesorderdetail cube: primary key for 'salesorderdetail' is required when join is defined
... (dozens more)

Root Cause

DevServer.ts calls driver.tablesSchema() in both the /playground/db-schema and /playground/generate-schema endpoints:

// Line 141
const tablesSchema = await driver.tablesSchema();

// Line 179
const tablesSchema = req.body.tablesSchema || (await driver.tablesSchema());

tablesSchema() only queries information_schema.columns and does not fetch primary key constraints. As a result, no column ever gets attributes: ['primaryKey'], so ScaffoldingSchema.dimensions() never sets isPrimaryKey: true, and BaseSchemaFormatter never emits primary_key: true.

The correct method is tablesSchemaV2(), which calls primaryKeys() (overridden in PostgresDriver with a real information_schema.table_constraints query) and merges the results into the column data with attributes: ['primaryKey'].

Steps to Reproduce

1. Connect Cube Playground to a PostgreSQL database (e.g. AdventureWorks)
2. Go to Data Model → Generate Data Model
3. Select any table with a join (e.g. sales.salesorderheader)
4. Click Generate
5. Observe the generated YAML has no primary_key: true dimension
6. Cube fails to compile with: primary key for 'X' is required when join is defined

Affected Tables / Columns

The bug affects all tables where the PK column name is not literally id. The scaffolding has a fallback heuristic fixCase(column.name) === 'id' but real-world tables use names like salesorderid, productid, businessentityid, etc.

Expected Behavior

Generated YAML should include the PK dimension marked as primary_key: true:

dimensions:
  - name: salesorderid
    sql: salesorderid
    type: number
    primary_key: true
    public: false

Fix

In packages/cubejs-server-core/src/core/DevServer.ts, replace both calls to tablesSchema() with tablesSchemaV2():

- const tablesSchema = await driver.tablesSchema();
+ const tablesSchema = await driver.tablesSchemaV2();

- const tablesSchema = req.body.tablesSchema || (await driver.tablesSchema());
+ const tablesSchema = req.body.tablesSchema || (await driver.tablesSchemaV2());

Environment

• Cube version: 1.6.23
• Database: PostgreSQL 14.10
• Database: AdventureWorks (timchapman/postgresql-adventureworks)