feat: add ColumnType struct and associated methods for database column metadata

cmd/go_migrate/colum-type.go

@@ -0,0 +1,40 @@
+package main
+
+type ColumnType struct {
+	name string
+
+	hasNullable       bool
+	hasMaxLength      bool
+	hasPrecisionScale bool
+
+	userType   string
+	systemType string
+	nullable   bool
+	maxLength  int64
+	precision  int64
+	scale      int64
+}
+
+func (c *ColumnType) Name() string {
+	return c.name
+}
+
+func (c *ColumnType) UserType() string {
+	return c.userType
+}
+
+func (c *ColumnType) SystemType() string {
+	return c.systemType
+}
+
+func (c *ColumnType) Length() (length int64, ok bool) {
+	return c.maxLength, c.hasMaxLength
+}
+
+func (c *ColumnType) DecimalSize() (precision, scale int64, ok bool) {
+	return c.precision, c.scale, c.hasPrecisionScale
+}
+
+func (c *ColumnType) Nullable() (nullable, ok bool) {
+	return c.nullable, c.hasNullable
+}