fix(#patch); Added return and warn when 2 input tokens are given in a swap; also fixed protocol getter.

[steegecs]

Context: Issue #1191 Added a warning when 2 input tokens are given in a swap. This is a very rare occurrence and would require us to make changes to the schema to handle properly. This serves as a temporary fix and ignores these swaps. I think this is okay since it is very rare that people provide 2 input tokens, and is not a normal use case of the DEX.

Additionally, I made a small fix on the protocol getter to remove an early .save() of the entity that was causing errors.