✨ integrates Dynamic ENUM Metadata within Rules

Summary:
This commit revolutionizes our approach to handling ENUM metadata for
rule input structures by embedding this metadata directly within each
rule's definition. By leveraging the `EnumProvider` interface and
utilizing reflection, we've created a system where rules self-describe
their ENUM fields, enhancing the API's flexibility and maintainability.

The `GetRuleStruct` API endpoint is now capable of dynamically generating
responses that include both the input structure and ENUM options, directly
derived from the rule definitions themselves.

Key Changes:
- **Introduced `EnumProvider` Interface**:
Allows rule structs to define their own ENUM options, centralizing this
information within the rule implementations.

- **Enhanced Rule Descriptors**:
Rule descriptors are streamlined to focus on factory methods and input
struct types, with ENUM metadata being provided by the rules themselves
through the `EnumProvider` interface.

- **Dynamic ENUM Metadata Retrieval**:
The `GetRuleStruct` function dynamically extracts ENUM metadata from
rules that implement the `EnumProvider`, ensuring the API response
includes relevant ENUM options for frontend UI generation.

- **API Response Enhancement**:
Adjusted the API to provide a response that includes the rule's input
structure, possible ENUM values, and the rule instance representation,
all derived dynamically to support extensible and maintainable rule
definitions.

rules/enum.go

@@ -0,0 +1,25 @@
+// Copyright 2024 Florian Beisel
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package rules
+
+type EnumFieldMetadata struct {
+	FieldName string
+	Values    []string
+}
+
+// EnumProvider interface that rules should implement if they provide enum values.
+type EnumProvider interface {
+	EnumOptions() []EnumFieldMetadata
+}