feature: support format field, such as timestamp to LocalDateTime

[javalover123]

First, Many thanks for opensource.

May support for second, milliseconds, nano to Local Date Time, or support user input a function body to handler a row. { "key": "key", "second": 1648776600, "timestamp": 1648776600000, "nano": 1648846800000007200 }

[rikimaru0345]

good idea, but hard to implement.

I think, what you suggested (user provided js function to preview a row) is pretty much the only way, because kowl can't know the format of the message (what fields are intended to be shown in which format).

Sure, I could add an option somewhere so you can select specific fields and they'll always be interpreted as some sort of datetime, but that will get out of hand very quickly...

Next would probably be supporting custom displays for various currencies, or maybe in some messages the timestamp is missing, and should be derived from some other field, ...

All in all, I think allowing user provided JS that will format/generate the preview of a message is the best solution. The "api" for that would of course contain methods to easily generate stuff that already exists, like those little tags/blobs (that currently contains each field-name)...

[javalover123]

Or add select format per field, such as timestamp to datetime.