Migrate to PostgreSQL and fix related issues

models/fields.go

@@ -11,8 +11,8 @@ type Field struct {
 	Name       string
 	PersonType string
 	FieldType  string
-	ListID     uint
-	List       List
+	ListID     *uint
+	List       *List
 	Position   int
 }
 
@@ -25,8 +25,8 @@ type FieldValue struct {
 	ValueString sql.NullString
 	ValueInt    sql.NullInt64
 	ValueDate   sql.NullTime
-	ListItemID  uint
-	ListItem    ListItem
+	ListItemID  *uint
+	ListItem    *ListItem
 }
 
 var PersonTypes = map[string]string{

models/sections.go

@@ -6,7 +6,7 @@ type Section struct {
 	gorm.Model
 	Name             string
 	ShortName        string
-	ParentSectionID  uint
+	ParentSectionID  *uint
 	ParentSection    *Section
 	ContainsMembers  bool
 	ContainsContacts bool