Add the datasource of RDBMS (PostgreSQL and MySQL)

pkg/models/datasource.go

@@ -16,6 +16,7 @@ const (
 	DS_CLOUDWATCH    = "cloudwatch"
 	DS_KAIROSDB      = "kairosdb"
 	DS_PROMETHEUS    = "prometheus"
+	DS_SQLDB         = "sqldb"
 	DS_ACCESS_DIRECT = "direct"
 	DS_ACCESS_PROXY  = "proxy"
 )
@@ -59,6 +60,7 @@ var knownDatasourcePlugins map[string]bool = map[string]bool{
 	DS_CLOUDWATCH:  true,
 	DS_PROMETHEUS:  true,
 	DS_OPENTSDB:    true,
+	DS_SQLDB:       true,
 	"opennms":      true,
 	"druid":        true,
 	"dalmatinerdb": true,