Why do ThingAttribute has value pattern that is not allowing plus(+) and space( )?

Hi. The allowed patterns, for both keys and values, are defined here: https://docs.aws.amazon.com/iot/latest/apireference/API_ThingAttribute.html

You can't use space or plus directly in Thing attributes. You could perhaps encode your attributes. Or you could perhaps store data instead in some other storage service and use that rather than Thing attributes.