feat(pgsql): ✨ Add templates for constraints and sequences

* Introduce new templates for creating unique, check, and foreign key constraints with existence checks.
* Add templates for setting sequence values and creating sequences.
* Refactor existing SQL generation logic to utilize new templates for better maintainability and readability.
* Ensure identifiers are properly quoted to handle special characters and reserved keywords.

pkg/writers/pgsql/template_functions_test.go

@@ -101,6 +101,31 @@ func TestSafeIdentifier(t *testing.T) {
 	}
 }
 
+func TestQuoteIdent(t *testing.T) {
+	tests := []struct {
+		input    string
+		expected string
+	}{
+		{"valid_name", "valid_name"},
+		{"ValidName", `"ValidName"`},
+		{"123column", `"123column"`},
+		{"215162_fk_constraint", `"215162_fk_constraint"`},
+		{"user-id", `"user-id"`},
+		{"user@domain", `"user@domain"`},
+		{`"quoted"`, `"""quoted"""`},
+		{"", `""`},
+		{"lowercase", "lowercase"},
+		{"with_underscore", "with_underscore"},
+	}
+
+	for _, tt := range tests {
+		result := quoteIdent(tt.input)
+		if result != tt.expected {
+			t.Errorf("quoteIdent(%q) = %q, want %q", tt.input, result, tt.expected)
+		}
+	}
+}
+
 func TestGoTypeToSQL(t *testing.T) {
 	tests := []struct {
 		input    string
@@ -243,7 +268,7 @@ func TestTemplateFunctions(t *testing.T) {
 	// Check that all expected functions are registered
 	expectedFuncs := []string{
 		"upper", "lower", "snake_case", "camelCase",
-		"indent", "quote", "escape", "safe_identifier",
+		"indent", "quote", "escape", "safe_identifier", "quote_ident",
 		"goTypeToSQL", "sqlTypeToGo", "isNumeric", "isText",
 		"first", "last", "filter", "mapFunc", "join_with",
 		"join",