ENH: Add JSON expressions ... path exists and value at path equals value

[rbygrave]

So Postgres and Oracle have JSON expressions and currently with Ebean you need to use a raw() expression to have these in your where clause like:

List<SimpleDoc> docs = SimpleDoc.find.where()
  .raw("jsonbExists(content#>'{docName}', 'My document')")
  .findList();

This enhancement would add 'path exists' and 'value at path equals ?' expressions to the ExpressionList to make this much nicer to use.

[rbygrave]

Expressions added are:

/**
 * Path exists - for the given path in a JSON document.
 */
ExpressionList<T> jsonExists(String propertyName, String path);

/**
 * Path does not exist - for the given path in a JSON document.
 */
ExpressionList<T> jsonNotExists(String propertyName, String path);

/**
 * Equal to expression for the value at the given path in the JSON document.
 */
ExpressionList<T> jsonEqualTo(String propertyName, String path, Object value);

/**
 * Not Equal to - for the given path in a JSON document.
 */
ExpressionList<T> jsonNotEqualTo(String propertyName, String path, Object val);

/**
 * Greater than - for the given path in a JSON document.
 */
ExpressionList<T> jsonGreaterThan(String propertyName, String path, Object val);

/**
 * Greater than or equal to - for the given path in a JSON document.
 */
ExpressionList<T> jsonGreaterOrEqual(String propertyName, String path, Object val);

/**
 * Less than - for the given path in a JSON document.
 */
ExpressionList<T> jsonLessThan(String propertyName, String path, Object val);

/**
 * Less than or equal to - for the given path in a JSON document.
 */
ExpressionList<T> jsonLessOrEqualTo(String propertyName, String path, Object val);