Correctly merge plugin configuration on mmctl config patch (#26647)

* Adds a step to the config patch command to merge plugin configurations

* Fix linter

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

server/cmd/mmctl/commands/utils_test.go

@@ -0,0 +1,101 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package commands
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestDeepMergeMaps(t *testing.T) {
+	testCases := []struct {
+		Name     string
+		Base     map[string]any
+		Patch    map[string]any
+		Expected map[string]any
+	}{
+		{
+			Name:     "Values of base doesn't exist in patch",
+			Base:     map[string]any{"Name": "John", "Surname": "Doe"},
+			Patch:    map[string]any{"Name": "Jane"},
+			Expected: map[string]any{"Name": "Jane", "Surname": "Doe"},
+		},
+		{
+			Name:     "Values of patch doesn't exist in base",
+			Base:     map[string]any{"Name": "John"},
+			Patch:    map[string]any{"Name": "Jane", "Surname": "Doe"},
+			Expected: map[string]any{"Name": "Jane", "Surname": "Doe"},
+		},
+		{
+			Name:     "Maps contain nested maps",
+			Base:     map[string]any{"Person": map[string]any{"Name": "John", "Surname": "Doe"}},
+			Patch:    map[string]any{"Person": map[string]any{"Name": "Jane"}, "Age": 27},
+			Expected: map[string]any{"Person": map[string]any{"Name": "Jane", "Surname": "Doe"}, "Age": 27},
+		},
+		{
+			Name:     "Values have different types",
+			Base:     map[string]any{"Person": "John Doe"},
+			Patch:    map[string]any{"Person": map[string]any{"Name": "John", "Surname": "Doe"}},
+			Expected: map[string]any{"Person": map[string]any{"Name": "John", "Surname": "Doe"}},
+		},
+		{
+			Name:     "Values have different types, reversed",
+			Base:     map[string]any{"Person": map[string]any{"Name": "John", "Surname": "Doe"}},
+			Patch:    map[string]any{"Person": "John Doe"},
+			Expected: map[string]any{"Person": "John Doe"},
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.Name, func(t *testing.T) {
+			require.Equal(t, DeepMergeMaps(tc.Base, tc.Patch), tc.Expected)
+		})
+	}
+}
+
+func TestMergePluginConfigs(t *testing.T) {
+	basePluginConfig := map[string]map[string]any{
+		"plugin.1": {
+			"First": "key",
+			"Second": map[string]any{
+				"nested": "key",
+			},
+		},
+		"plugin.2": {
+			"Name": "John",
+		},
+	}
+
+	patchPluginConfig := map[string]map[string]any{
+		"plugin.1": {
+			"Second": map[string]any{
+				"nested": false,
+				"new":    1,
+			},
+		},
+		"plugin.3": {
+			"New": "plugin",
+		},
+	}
+
+	expectedPluginConfig := map[string]map[string]any{
+		"plugin.1": {
+			"First": "key",
+			"Second": map[string]any{
+				"nested": false,
+				"new":    1,
+			},
+		},
+		"plugin.2": {
+			"Name": "John",
+		},
+		"plugin.3": {
+			"New": "plugin",
+		},
+	}
+
+	mergedPluginConfigs := MergePluginConfigs(basePluginConfig, patchPluginConfig)
+	require.Equal(t, expectedPluginConfig, mergedPluginConfigs)
+}