Non-standard single-quoted JSON keys in YearMonthField.setMin/setMax

[javier-godoy]

Describe the bug

setMin() and setMax() build a JSON string with single-quoted keys:

Json.parse("{'month': " + min.getMonth().ordinal() + ", 'year': " + min.getYear() + "}")

Single-quoted keys are not valid per the JSON specification. This currently works because the Elemental2 Json.parse() implementation is lenient, but it relies on undocumented behaviour.

Expected behavior

Keys should be double-quoted:

Json.parse(String.format("{\"month\": %d, \"year\": %d}", min.getMonth().ordinal(), min.getYear()))

Add-on Version

4.6.1-SNAPSHOT

Vaadin Version

N/A