Backend Plugins: Provide proper plugin config to plugins (#21985)

Properly provides plugin configs to backend plugins.
Uses v0.16.0 of grafana-plugin-sdk-go-

Ref #21512
Ref #19667

pkg/models/plugin_setting_cache_test.go

@@ -0,0 +1,62 @@
+package models
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/grafana/grafana/pkg/components/securejsondata"
+)
+
+func TestPluginSettingDecryptionCache(t *testing.T) {
+	t.Run("When plugin settings hasn't been updated, encrypted JSON should be fetched from cache", func(t *testing.T) {
+		ClearPluginSettingDecryptionCache()
+
+		ps := PluginSetting{
+			Id:       1,
+			JsonData: map[string]interface{}{},
+			SecureJsonData: securejsondata.GetEncryptedJsonData(map[string]string{
+				"password": "password",
+			}),
+		}
+
+		// Populate cache
+		password, ok := ps.DecryptedValue("password")
+		require.Equal(t, "password", password)
+		require.True(t, ok)
+
+		ps.SecureJsonData = securejsondata.GetEncryptedJsonData(map[string]string{
+			"password": "",
+		})
+
+		require.Equal(t, "password", password)
+		require.True(t, ok)
+	})
+
+	t.Run("When plugin settings is updated, encrypted JSON should not be fetched from cache", func(t *testing.T) {
+		ClearPluginSettingDecryptionCache()
+
+		ps := PluginSetting{
+			Id:       1,
+			JsonData: map[string]interface{}{},
+			SecureJsonData: securejsondata.GetEncryptedJsonData(map[string]string{
+				"password": "password",
+			}),
+		}
+
+		// Populate cache
+		password, ok := ps.DecryptedValue("password")
+		require.Equal(t, "password", password)
+		require.True(t, ok)
+
+		ps.SecureJsonData = securejsondata.GetEncryptedJsonData(map[string]string{
+			"password": "",
+		})
+		ps.Updated = time.Now()
+
+		password, ok = ps.DecryptedValue("password")
+		require.Empty(t, password)
+		require.True(t, ok)
+	})
+}