Add field_quote for TextQueryBackend in Equal Expression

[nNipsx-Sec]

In some case of SIEM, the field have a whitespace example: File Name so it's need add quote to define fields name. We can add this quote to some expression but can't add field quote to equal expression.

So my solution is add 1 field_quote like as a str_quote.

field_quote       : ClassVar[str] = "" 

[thomaspatzke]

Oh, yes, this is a gap...I will implement this in the TextQueryBackend base class!

[nNipsx-Sec]

Thanks it's need to Qradar backend, waiting for this.

[thomaspatzke]

Merged your PR, extended it and fixed some issues in other affected areas, now it's in release 0.6.2!

[nNipsx-Sec]

Great thanks for add more extended code.