implement "OR" filtering

[jamesdixon]

@alechirsch I know we had briefly discussed a possible API to handle the case when you want to filter on x OR y rather than x AND y.

Want to restart that discussion here and figure out an API?

[alechirsch]

Sure, I'd be happy to discuss it

[ErisDS]

Throwing in an idea here:

Ghost has a filter query language that works with JSON API's ?filter= query param and supports OR queries, it's called GQL. The syntax is based on the filtering available in gmail, github and slack.

An example would be ?filter=foo:bar,bar:foo - a comma denotes an OR. ?filter=foo:bar+bar:foo - a plus denotes an AND. It does require URL encoding, however it's super flexible.

It's a bit unloved and needs a rewrite to squash some serious bugs in the first iteration, however as it's a simpler, shorter, slightly more powerful syntax I'd love to see more people make use of it.

Support could be added in this lib and in https://github.com/kideh88/node-jsonapi-query-parser.

[alechirsch]

#63