feat(bun): generate native Go array slices for PostgreSQL array columns

Bun's pgdialect scans/appends native slices directly, so array columns
(text[], integer[], uuid[], ...) always generate as plain []string,
[]int32, etc. with an explicit "array" bun tag, regardless of --types
(sqltypes/stdlib/baselib). The SqlXxxArray wrapper types are no longer
used for Bun array columns (gorm is unaffected and keeps using them).

Adds --array-nullable pointer_slice to represent nullable array columns
as *[]T instead of []T, so callers can distinguish SQL NULL (nil) from
'{}' (pointer to an empty slice). Verified end-to-end against a live
PostgreSQL instance for NULL/{}/populated arrays in every --types mode.

Closes #13

vendor/github.com/uptrace/bun/migrate/sqlschema/database.go

@@ -0,0 +1,128 @@
+package sqlschema
+
+import (
+	"slices"
+	"strings"
+
+	"github.com/uptrace/bun/schema"
+)
+
+type Database interface {
+	GetTables() []Table
+	GetForeignKeys() map[ForeignKey]string
+}
+
+var _ Database = (*BaseDatabase)(nil)
+
+// BaseDatabase is a base database definition.
+//
+// Dialects and only dialects can use it to implement the Database interface.
+// Other packages must use the Database interface.
+type BaseDatabase struct {
+	Tables      []Table
+	ForeignKeys map[ForeignKey]string
+}
+
+func (ds BaseDatabase) GetTables() []Table {
+	return ds.Tables
+}
+
+func (ds BaseDatabase) GetForeignKeys() map[ForeignKey]string {
+	return ds.ForeignKeys
+}
+
+// ForeignKey represents a foreign key constraint between two tables.
+type ForeignKey struct {
+	From ColumnReference
+	To   ColumnReference
+}
+
+func NewColumnReference(tableName string, columns ...string) ColumnReference {
+	return ColumnReference{
+		TableName: tableName,
+		Column:    NewColumns(columns...),
+	}
+}
+
+func (fk ForeignKey) DependsOnTable(tableName string) bool {
+	return fk.From.TableName == tableName || fk.To.TableName == tableName
+}
+
+func (fk ForeignKey) DependsOnColumn(tableName string, column string) bool {
+	return fk.DependsOnTable(tableName) &&
+		(fk.From.Column.Contains(column) || fk.To.Column.Contains(column))
+}
+
+// Columns is a hashable representation of []string used to define schema constraints that depend on multiple columns.
+// Although having duplicated column references in these constraints is illegal, Columns neither validates nor enforces this constraint on the caller.
+type Columns string
+
+// NewColumns creates a composite column from a slice of column names.
+func NewColumns(columns ...string) Columns {
+	slices.Sort(columns)
+	return Columns(strings.Join(columns, ","))
+}
+
+func (c *Columns) String() string {
+	return string(*c)
+}
+
+func (c *Columns) AppendQuery(gen schema.QueryGen, b []byte) ([]byte, error) {
+	return schema.Safe(*c).AppendQuery(gen, b)
+}
+
+// Split returns a slice of column names that make up the composite.
+func (c *Columns) Split() []string {
+	return strings.Split(c.String(), ",")
+}
+
+// ContainsColumns checks that columns in "other" are a subset of current colums.
+func (c *Columns) ContainsColumns(other Columns) bool {
+	columns := c.Split()
+Outer:
+	for _, check := range other.Split() {
+		for _, column := range columns {
+			if check == column {
+				continue Outer
+			}
+		}
+		return false
+	}
+	return true
+}
+
+// Contains checks that a composite column contains the current column.
+func (c *Columns) Contains(other string) bool {
+	return c.ContainsColumns(Columns(other))
+}
+
+// Replace renames a column if it is part of the composite.
+// If a composite consists of multiple columns, only one column will be renamed.
+func (c *Columns) Replace(oldColumn, newColumn string) bool {
+	columns := c.Split()
+	for i, column := range columns {
+		if column == oldColumn {
+			columns[i] = newColumn
+			*c = NewColumns(columns...)
+			return true
+		}
+	}
+	return false
+}
+
+// Unique represents a unique constraint defined on 1 or more columns.
+type Unique struct {
+	Name    string
+	Columns Columns
+}
+
+// Equals checks that two unique constraint are the same, assuming both are defined for the same table.
+func (u Unique) Equals(other Unique) bool {
+	return u.Columns == other.Columns
+}
+
+// ColumnReference identifies a column or set of columns in a table.
+type ColumnReference struct {
+	TableName string
+	Column    Columns
+}