Add a metadata system

internal/models/metadata.go

@@ -0,0 +1,13 @@
+package models
+
+// MetadataTable is the name of the table the 'Metadatum' model is stored in.
+const MetadataTable = "metadatum"
+
+// Metadatum represents
+type Metadatum struct {
+	Pk uint `gorm:"column:pk;primaryKey"`
+
+	Key   string `gorm:"column:key;not null"` // key for the value, see the keys below
+	Slug  string `gorm:"column:slug"`         // optional slug of instance
+	Value []byte `gorm:"column:value"`        // serialized json value of the data
+}