`t:Hammer.key/0` is `term()`, but all backend expect `String.t()`

[Gladear]

Describe the bug

Hammer.key/0 is set to value term(), so we should be able to add any key.
However, in all backends (e.g. ETS.FixWindows, Atomic.LeakyBucket, Redis.TokenBucket), @spec of implementations require the key to be a string. More importantly, while non-binary values do work in most backends, the Redis one actually require the key to be a string, and crashes otherwise.

** Provide the following details

• Version of the library: 7.0.1
• Backend used: *
• Algorithm used: *
• Elixir version (elixir -v): N/A
• Erlang version (erl -v): N/A
• Operating system: N/A

Expected behavior

Should the backend work with any term? Or should the key be updated to be a string? Having any term as key can be pretty useful, but does not seem to fit all backends.

I'm open to make the required changes in a PR, but I'd rather wait a decision on the matter beforehand 😄

[epinault]

thanks for reporting this! I am not sure if there is a need of non string key and I am open to it. I would prefer to make them term in most and just limit redis to be a string would be my direction. Which means it s still a term just restricted to string in redis only