feat: auto generated files and new structure (#4)

## Description

<!-- **Please link some issue here describing what you are trying to achieve.**

In case there is no issue present for your PR, please consider creating one.
At least please give us some description what you are trying to achieve and why your change is needed. -->

relates to #1234

## Checklist

- [ ] Issue was linked above
- [ ] Code format was applied: `make fmt`
- [ ] Examples were added / adjusted (see `examples/` directory)
- [x] Docs are up-to-date: `make generate-docs` (will be checked by CI)
- [ ] Unit tests got implemented or updated
- [ ] Acceptance tests got implemented or updated (see e.g. [here](f5f99d1709/stackit/internal/services/dns/dns_acc_test.go))
- [x] Unit tests are passing: `make test` (will be checked by CI)
- [x] No linter issues: `make lint` (will be checked by CI)

Reviewed-on: #4
Reviewed-by: Andre_Harms <andre.harms@stackit.cloud>
Co-authored-by: Marcel S. Henselin <marcel.henselin@stackit.cloud>
Co-committed-by: Marcel S. Henselin <marcel.henselin@stackit.cloud>

stackit/internal/services/postgresflexalpha/utils/planModifiers.go

@@ -0,0 +1,229 @@
+package utils
+
+import (
+	"fmt"
+	"log/slog"
+	"reflect"
+	"slices"
+
+	"github.com/hashicorp/terraform-plugin-framework/resource/schema"
+	"github.com/hashicorp/terraform-plugin-framework/resource/schema/boolplanmodifier"
+	"github.com/hashicorp/terraform-plugin-framework/resource/schema/int64planmodifier"
+	"github.com/hashicorp/terraform-plugin-framework/resource/schema/listplanmodifier"
+	"github.com/hashicorp/terraform-plugin-framework/resource/schema/stringplanmodifier"
+	"github.com/iancoleman/strcase"
+
+	"gopkg.in/yaml.v3"
+)
+
+type Field struct {
+	Name      string    `yaml:"name"`
+	Modifiers []*string `yaml:"modifiers"`
+}
+
+type Fields struct {
+	Fields []*Field `yaml:"fields"`
+}
+
+var validModifiers = []string{
+	"UseStateForUnknown",
+	"RequiresReplace",
+}
+
+func ReadModifiersConfig(content []byte) (*Fields, error) {
+	var fields Fields
+	err := yaml.Unmarshal(content, &fields)
+	if err != nil {
+		return nil, err
+	}
+	return &fields, nil
+}
+
+func AddPlanModifiersToResourceSchema(fields *Fields, s *schema.Schema) error {
+	err := validateFields(fields)
+	if err != nil {
+		return err
+	}
+
+	resAttr, err := handleAttributes("", s.Attributes, fields)
+	if err != nil {
+		return err
+	}
+	s.Attributes = resAttr
+
+	return nil
+}
+
+func handleAttributes(prefix string, attributes map[string]schema.Attribute, fields *Fields) (map[string]schema.Attribute, error) {
+	fieldMap := fieldListToMap(fields)
+	for attrName, attrValue := range attributes {
+		attrNameSnake := strcase.ToSnake(attrName)
+		if prefix != "" {
+			attrNameSnake = prefix + "." + attrNameSnake
+		}
+		switch reflect.TypeOf(attrValue).String() {
+		case "schema.BoolAttribute":
+			if field, ok := fieldMap[attrNameSnake]; ok {
+				res, err := handleBoolPlanModifiers(attrValue, field)
+				if err != nil {
+					return nil, err
+				}
+				attributes[attrName] = res
+			}
+		case "schema.Int64Attribute":
+			if field, ok := fieldMap[attrNameSnake]; ok {
+				res, err := handleInt64PlanModifiers(attrValue, field)
+				if err != nil {
+					return nil, err
+				}
+				attributes[attrName] = res
+			}
+		case "schema.StringAttribute":
+			if field, ok := fieldMap[attrNameSnake]; ok {
+				res, err := handleStringPlanModifiers(attrValue, field)
+				if err != nil {
+					return nil, err
+				}
+				attributes[attrName] = res
+			}
+		case "schema.ListAttribute":
+			if field, ok := fieldMap[attrNameSnake]; ok {
+				res, err := handleListPlanModifiers(attrValue, field)
+				if err != nil {
+					return nil, err
+				}
+				attributes[attrName] = res
+			}
+		case "schema.SingleNestedAttribute":
+			nested, ok := attrValue.(schema.SingleNestedAttribute)
+			if !ok {
+				if _, ok := attrValue.(interface {
+					GetAttributes() map[string]schema.Attribute
+				}); ok {
+					return nil, fmt.Errorf("unsupported type for single nested attribute")
+				}
+			}
+
+			res, err := handleAttributes(attrName, nested.Attributes, fields)
+			if err != nil {
+				return nil, err
+			}
+			nested.Attributes = res
+			attributes[attrName] = nested
+		default:
+			slog.Warn("type currently not supported", "type", reflect.TypeOf(attrValue).String())
+		}
+	}
+	return attributes, nil
+}
+
+func handleBoolPlanModifiers(
+	attr schema.Attribute,
+	fields []*string,
+) (schema.Attribute, error) {
+	a, ok := attr.(schema.BoolAttribute)
+	if !ok {
+		return nil, fmt.Errorf("field is not a string attribute")
+	}
+
+	for _, v := range fields {
+		switch *v {
+		case "RequiresReplace":
+			a.PlanModifiers = append(a.PlanModifiers, boolplanmodifier.RequiresReplace())
+		case "UseStateForUnknown":
+			a.PlanModifiers = append(a.PlanModifiers, boolplanmodifier.UseStateForUnknown())
+		}
+	}
+	return a, nil
+}
+
+func handleStringPlanModifiers(
+	attr schema.Attribute,
+	fields []*string,
+) (schema.Attribute, error) {
+	a, ok := attr.(schema.StringAttribute)
+	if !ok {
+		return nil, fmt.Errorf("field is not a string attribute")
+	}
+
+	for _, v := range fields {
+		switch *v {
+		case "RequiresReplace":
+			a.PlanModifiers = append(a.PlanModifiers, stringplanmodifier.RequiresReplace())
+		case "UseStateForUnknown":
+			a.PlanModifiers = append(a.PlanModifiers, stringplanmodifier.UseStateForUnknown())
+		}
+	}
+	return a, nil
+}
+
+func handleInt64PlanModifiers(
+	attr schema.Attribute,
+	fields []*string,
+) (schema.Attribute, error) {
+	a, ok := attr.(schema.Int64Attribute)
+	if !ok {
+		return nil, fmt.Errorf("field is not a string attribute")
+	}
+
+	for _, v := range fields {
+		switch *v {
+		case "RequiresReplace":
+			a.PlanModifiers = append(a.PlanModifiers, int64planmodifier.RequiresReplace())
+		case "UseStateForUnknown":
+			a.PlanModifiers = append(a.PlanModifiers, int64planmodifier.UseStateForUnknown())
+		}
+	}
+	return a, nil
+}
+
+func handleListPlanModifiers(
+	attr schema.Attribute,
+	fields []*string,
+) (schema.Attribute, error) {
+	a, ok := attr.(schema.ListAttribute)
+	if !ok {
+		return nil, fmt.Errorf("field is not a string attribute")
+	}
+
+	for _, v := range fields {
+		switch *v {
+		case "RequiresReplace":
+			a.PlanModifiers = append(a.PlanModifiers, listplanmodifier.RequiresReplace())
+		case "UseStateForUnknown":
+			a.PlanModifiers = append(a.PlanModifiers, listplanmodifier.UseStateForUnknown())
+		}
+	}
+	return a, nil
+}
+
+func validateFields(fields *Fields) error {
+	if fields == nil {
+		return nil
+	}
+	for _, field := range fields.Fields {
+		for _, modifier := range field.Modifiers {
+			if *modifier == "" {
+				return fmt.Errorf("modifier %s is required", *modifier)
+			}
+			if !slices.Contains(validModifiers, *modifier) {
+				return fmt.Errorf("modifier %s is invalid", *modifier)
+			}
+		}
+	}
+	return nil
+}
+
+func fieldListToMap(fields *Fields) map[string][]*string {
+	res := make(map[string][]*string)
+
+	if fields != nil {
+		for _, field := range fields.Fields {
+			res[field.Name] = field.Modifiers
+		}
+	} else {
+		slog.Warn("no fields available")
+	}
+
+	return res
+}