feat(mssql): add MSSQL writer for generating DDL from database schema

- Implement MSSQL writer to generate SQL scripts for creating schemas, tables, and constraints.
- Support for identity columns, indexes, and extended properties.
- Add tests for column definitions, table creation, primary keys, foreign keys, and comments.
- Include testing guide and sample schema for integration tests.

pkg/readers/mssql/README.md

@@ -0,0 +1,91 @@
+# MSSQL Reader
+
+Reads database schema from Microsoft SQL Server databases using a live connection.
+
+## Features
+
+- **Live Connection**: Connects to MSSQL databases using the Microsoft ODBC driver
+- **Multi-Schema Support**: Reads multiple schemas with full support for user-defined schemas
+- **Comprehensive Metadata**: Reads tables, columns, constraints, indexes, and extended properties
+- **Type Mapping**: Converts MSSQL types to canonical types for cross-database compatibility
+- **Extended Properties**: Extracts table and column descriptions from MS_Description
+- **Identity Columns**: Maps IDENTITY columns to AutoIncrement
+- **Relationships**: Derives relationships from foreign key constraints
+
+## Connection String Format
+
+```
+sqlserver://[user[:password]@][host][:port][?query]
+```
+
+Examples:
+```
+sqlserver://sa:password@localhost/dbname
+sqlserver://user:pass@192.168.1.100:1433/production
+sqlserver://localhost/testdb?encrypt=disable
+```
+
+## Supported Constraints
+
+- Primary Keys
+- Foreign Keys (with ON DELETE and ON UPDATE actions)
+- Unique Constraints
+- Check Constraints
+
+## Type Mappings
+
+| MSSQL Type | Canonical Type |
+|------------|----------------|
+| INT | int |
+| BIGINT | int64 |
+| SMALLINT | int16 |
+| TINYINT | int8 |
+| BIT | bool |
+| REAL | float32 |
+| FLOAT | float64 |
+| NUMERIC, DECIMAL | decimal |
+| NVARCHAR, VARCHAR | string |
+| DATETIME2 | timestamp |
+| DATETIMEOFFSET | timestamptz |
+| UNIQUEIDENTIFIER | uuid |
+| VARBINARY | bytea |
+| DATE | date |
+| TIME | time |
+
+## Usage
+
+```go
+import "git.warky.dev/wdevs/relspecgo/pkg/readers/mssql"
+import "git.warky.dev/wdevs/relspecgo/pkg/readers"
+
+reader := mssql.NewReader(&readers.ReaderOptions{
+    ConnectionString: "sqlserver://sa:password@localhost/mydb",
+})
+
+db, err := reader.ReadDatabase()
+if err != nil {
+    panic(err)
+}
+
+// Process schema...
+for _, schema := range db.Schemas {
+    fmt.Printf("Schema: %s\n", schema.Name)
+    for _, table := range schema.Tables {
+        fmt.Printf("  Table: %s\n", table.Name)
+    }
+}
+```
+
+## Testing
+
+Run tests with:
+```bash
+go test ./pkg/readers/mssql/...
+```
+
+For integration testing with a live MSSQL database:
+```bash
+docker-compose up -d mssql
+go test -tags=integration ./pkg/readers/mssql/...
+docker-compose down
+```