Rails helpers/Liquid filters compatibility

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Target: Undecided

Rails provides a lot of helper functions by default. Some of them are directly usable as Liquid filters, some not. This specification aims to increase the compatibility between Rails helpers (both those included in Rails as those you can download to plug into existing RoR applications) and the Liquid filter system. It should be easy to use a Rails helper as a Liquid filter, and documentation on this should be available.