Boolean filtering support

[slemrmartin]

Filter supports only string and int filtering.

Boolean would be handly for avalability checks to ask for less data if more endpoints available

https://github.com/RedHatInsights/insights-api-common-rails/blob/master/lib/insights/api/common/filter.rb

[syncrou]

@mkanoor @bzwei do you have any thoughts on this?

[mkanoor]

@syncrou @abellotti mentioned that there is already a pattern in the filter.rb which we can extend to support booleans. We have
https://github.com/RedHatInsights/sources-api/blob/1bc1d8da8aed4d188d5eb5cb0725a3d80038b041/public/doc/openapi-3-v3.0.json#L1705
Which uses a boolean field but it's not being filtered on.