Add TreeModel and HasSubtree implementation

src/orm/dialect/PostgreSQLDialect.ts

@@ -316,6 +316,8 @@ export class PostgreSQLDialect extends SQLDialect {
                     const field: string = constraint.field.split('.').map(x => `"${x}"`)
                         .join('.')
                     statements.push(`${indent}${statements.length < 1 ? '' : constraint.preop + ' '}${field} ${constraint.operator} ${this.escape(constraint.operand).value}`)
+                } else if ( constraint instanceof QuerySafeValue ) {
+                    statements.push(`${indent}${statements.length < 1 ? '' : 'AND '}${constraint.toString()}`)
                 }
             }
 

src/orm/dialect/SQLDialect.ts

@@ -14,7 +14,7 @@ export type EscapeValue = null | undefined | string | number | boolean | Date |
 export type EscapeValueObject = { [field: string]: EscapeValue }
 
 /**
- * A wrapper class whose value is save to inject directly into a query.
+ * A wrapper class whose value is safe to inject directly into a query.
  */
 export class QuerySafeValue {
     constructor(