feat(ext): add Oracle and SQL Server database support

[timveil]

Roadmap item: Additional database support (Oracle, SQL Server).

Background

Database support is an SPI: DatabaseSupport (interface) + AbstractDatabaseSupport (a Map<JDBCType, GeneratorFactory> registry seeded by registerDefaults(), customized via the configure(Map) hook). Selection is DatabaseSupport.forProduct(productName) — a case-insensitive substring match that today knows cockroach, mysql, postgres, else DefaultSupport. The library itself is driver-agnostic (JDBC drivers are test-scoped only).

Adding a database = a new *Support subclass with a configure() override + a forProduct branch + integration coverage. The recent PostgreSQL/MySQL work (#444) is the template, including the empirical discovery step (dump DATA_TYPE/TYPE_NAME per column from the real driver before coding the dispatch).

Scope

OracleSupport

The hard part is Oracle's type model:

• NUMBER is the single numeric type — map by precision/scale (scale 0 → integer-family, else BigDecimal). maxDigits/maxSize from metadata drive this.
• VARCHAR2, NVARCHAR2, CHAR, NCHAR → string generators
• CLOB, NCLOB, BLOB, RAW/LONG RAW
• DATE (Oracle DATE includes time-of-day), TIMESTAMP, TIMESTAMP WITH [LOCAL] TIME ZONE
• BINARY_FLOAT, BINARY_DOUBLE
• INTERVAL YEAR TO MONTH, INTERVAL DAY TO SECOND
• No native BOOLEAN before Oracle 23c (23c adds it) — decide target version
• ojdbc surfaces several types via oracle.jdbc.OracleTypes; confirm empirically

Driver: com.oracle.database.jdbc:ojdbc11 (test). Container: org.testcontainers:oracle-free (gvenzl/oracle-free image).

SQLServerSupport

• UNIQUEIDENTIFIER (GUID string — reuse/extend UUIDGenerator)
• BIT → boolean; TINYINT is unsigned 0–255 (matches the existing default generator)
• DATETIME, DATETIME2, SMALLDATETIME, DATETIMEOFFSET, DATE, TIME
• MONEY, SMALLMONEY
• NVARCHAR, NCHAR, NTEXT, VARBINARY, IMAGE
• XML (reuse XmlGenerator)
• CLR types HIERARCHYID, GEOGRAPHY, GEOMETRY → out of scope; should throw UnsupportedOperationException (consistent with how unsupported PG/MySQL types behave today)

Driver: com.microsoft.sqlserver:mssql-jdbc (test). Container: org.testcontainers:mssqlserver (requires acceptLicense()).

Shared

• DatabaseSupport.forProduct: add oracle and microsoft sql server/sqlserver branches + cases in DatabaseSupportSelectionTest.
• create_tables.{oracle,sqlserver}.sql comprehensive type schemas + fillTestTables integration tests (mirror PostgresFillerTest/MySqlFillerTest).
• Unit coverage in DatabaseSupportTest for the new dispatch.

Acceptance criteria

• OracleSupport + SQLServerSupport registered and selectable via forProduct
• Comprehensive type schemas fill cleanly on real containers (latest GA server versions)
• Unsupported vendor types throw UnsupportedOperationException rather than generating invalid data
• README "Database Support" table updated

Notes

Worth splitting into two PRs (one per database) — each needs its own driver, container, and EULA/image considerations. Oracle NUMBER mapping is the main design risk; do the empirical discovery dump first.