[MsSql] Exclude generated columns from INSERT column list

[valerii-kuzivanov]

Fixes #5881

Problem

The MSSQL dialect's buildInsertQuery emits every table column in the INSERT column list, filling missing values with the default keyword. MsSqlColumn overrides shouldDisableInsert() with a hardcoded false, so generatedAlwaysAs() (computed) columns are included too — and SQL Server rejects any mention of a computed column in an INSERT column list, even with DEFAULT:

Msg 271: The column "value_upper" cannot be modified because it is either a computed column or is the result of a UNION operator.

const docs = mssqlTable('docs', {
	id: int().identity(),
	value: nvarchar({ length: 'max' }).notNull(),
	valueUpper: nvarchar('value_upper', { length: 450 }).generatedAlwaysAs(sql`upper([value])`),
});

db.insert(docs).values({ value: 'hello' }).toSQL().sql;
// before: insert into [docs] ([value], [value_upper]) values (@par0, default)  → Msg 271
// after:  insert into [docs] ([value]) values (@par0)

This blocks inserting into any table with a computed column — including schemas produced by drizzle-kit pull, which introspects SQL Server computed columns into generatedAlwaysAs().

Fix

• Remove the MsSqlColumn.shouldDisableInsert() override so the base Column logic applies (the MSSQL generatedAlwaysAs() builder always sets generated.type: 'always', so computed columns are excluded). No other dialect overrides this method on its base column class.
• MsSqlColumnWithIdentity.shouldDisableInsert() now combines its identity exclusion with the inherited check.

Tests

• Added insert into table with generated column to integration-tests/tests/mssql/mssql.test.ts: creates a table with a computed column, inserts through the query builder, and reads the computed value back. Fails with Msg 271 before the fix, passes after.
• Full MSSQL integration suite is green locally against mcr.microsoft.com/azure-sql-edge: mssql.test.ts 159 passed / 0 failed; mssql.custom.test.ts + mssql.prefixed.test.ts + mssql.rels.test.ts 186 passed / 0 failed.