Context

A few more combinators needed for this and other MRs:

Add more tup combinators.
Fix tup combinators to encode under distinct keys 0, 1, 2, ... corresponding to the index of the elements in the tuple. That is to avoid name clashes when composing encoders with overlapping keys.
Introduce a case_lwt combinator.
Introduce an option combinator.
Add tests for the new combinators.

Manually testing the MR

dune exec src/lib_scoru_wasm/test/test_scoru_wasm.exe -- test "$Encodings^"

Document the interface of any function added or modified (see the coding guidelines)
Document any change to the user interface, including configuration parameters (see node configuration)
Provide automatic testing (see the testing guide).
For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
Select suitable reviewers using the Reviewers field below.
Select as Assignee the next person who should take action on that MR

Edited Jul 19, 2022 by Joel Bjornson