feat: Support multiple configuration files (#396)

* Revert "Revert "feat: Support multiple configuration files" (#395)"

This reverts commit 87740e74a6.

* feat: Properly implement support for config directory

vendor/github.com/TwiN/deepmerge/.gitattributes

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+* text=auto eol=lf

vendor/github.com/TwiN/deepmerge/.gitignore

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+# IDE
+*.iml
+.idea
+.vscode
+
+# OS
+.DS_Store
+
+# JS
+node_modules
+
+# Go
+/vendor

vendor/github.com/TwiN/deepmerge/LICENSE

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+MIT License
+
+Copyright (c) 2023 TwiN
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

vendor/github.com/TwiN/deepmerge/README.md

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+# deepmerge
+![test](https://github.com/TwiN/deepmerge/workflows/test/badge.svg?branch=master)
+
+Go library for deep merging YAML files.
+
+
+## Usage
+```go
+package main
+
+import (
+	"github.com/TwiN/deepmerge"
+)
+
+func main() {
+	dst := `
+debug: true
+client:
+  insecure: true
+users:
+  - id: 1
+    firstName: John
+    lastName: Doe
+  - id: 2
+    firstName: Jane
+    lastName: Doe`
+	src := `
+client:
+  timeout: 5s
+users:
+  - id: 3
+    firstName: Bob
+    lastName: Smith`
+
+	output, err := deepmerge.YAML([]byte(dst), []byte(src))
+	if err != nil {
+		panic(err)
+	}
+	println(string(output))
+}
+```
+
+Output:
+```yaml
+client:
+    insecure: true
+    timeout: 5s
+debug: true
+users:
+    - firstName: John
+      id: 1
+      lastName: Doe
+    - firstName: Jane
+      id: 2
+      lastName: Doe
+    - firstName: Bob
+      id: 3
+      lastName: Smith
+```

vendor/github.com/TwiN/deepmerge/yaml.go

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+package deepmerge
+
+import (
+	"errors"
+
+	"gopkg.in/yaml.v3"
+)
+
+var (
+	ErrDeepMergeDuplicatePrimitiveKey = errors.New("error deep merging YAML files due to duplicate primitive key: only maps and slices/arrays can be merged, which means you cannot have define the same key twice for parameters that are not maps or slices/arrays")
+)
+
+type Config struct {
+	// PreventDuplicateKeysWithPrimitiveValue causes YAML to return an error if dst and src define the same key if
+	// said key has a value with a primitive type
+	// This does not apply to slices or maps. Defaults to true
+	PreventDuplicateKeysWithPrimitiveValue bool
+}
+
+// YAML merges the contents of src into dst
+func YAML(dst, src []byte, optionalConfig ...Config) ([]byte, error) {
+	var cfg Config
+	if len(optionalConfig) > 0 {
+		cfg = optionalConfig[0]
+	} else {
+		cfg = Config{PreventDuplicateKeysWithPrimitiveValue: true}
+	}
+	var dstMap, srcMap map[string]interface{}
+	err := yaml.Unmarshal(dst, &dstMap)
+	if err != nil {
+		return nil, err
+	}
+	err = yaml.Unmarshal(src, &srcMap)
+	if err != nil {
+		return nil, err
+	}
+	if dstMap == nil {
+		dstMap = make(map[string]interface{})
+	}
+	if err = deepMerge(dstMap, srcMap, cfg); err != nil {
+		return nil, err
+	}
+	return yaml.Marshal(dstMap)
+}
+
+func deepMerge(dst, src map[string]interface{}, config Config) error {
+	for srcKey, srcValue := range src {
+		if srcValueAsMap, ok := srcValue.(map[string]interface{}); ok { // handle maps
+			if dstValue, ok := dst[srcKey]; ok {
+				if dstValueAsMap, ok := dstValue.(map[string]interface{}); ok {
+					err := deepMerge(dstValueAsMap, srcValueAsMap, config)
+					if err != nil {
+						return err
+					}
+					continue
+				}
+			} else {
+				dst[srcKey] = make(map[string]interface{})
+			}
+			err := deepMerge(dst[srcKey].(map[string]interface{}), srcValueAsMap, config)
+			if err != nil {
+				return err
+			}
+		} else if srcValueAsSlice, ok := srcValue.([]interface{}); ok { // handle slices
+			if dstValue, ok := dst[srcKey]; ok {
+				if dstValueAsSlice, ok := dstValue.([]interface{}); ok {
+					// If both src and dst are slices, we'll copy the elements from that src slice over to the dst slice
+					dst[srcKey] = append(dstValueAsSlice, srcValueAsSlice...)
+					continue
+				}
+			}
+			dst[srcKey] = srcValueAsSlice
+		} else { // handle primitives
+			if config.PreventDuplicateKeysWithPrimitiveValue {
+				if _, ok := dst[srcKey]; ok {
+					return ErrDeepMergeDuplicatePrimitiveKey
+				}
+			}
+			dst[srcKey] = srcValue
+		}
+	}
+	return nil
+}