- add `generate_proxy_keys` endpoint to the Signer API. Modify the signer client accordingly.

- add a `.dockerignore` file

- remove the need for modules to provide their id in requests. A module's JWT is now solely sufficient to identify the module.
  * `SigningService` now contains jwt <-> module_id in a bidirectional hashmap

- add authentication middleware to the signer service instead of manual auth in the handlers

- introduce `ModuleId` and `Jwt` wrapper types around strings to improve semantics (useful after a couple of mishaps with key <-> value directions across the different maps)
  * see `common::types`

- add example proxy key generation request in `da_commit` module

- small misc changes

- small reformatting

* make `crates::common::signature::random_secret()` infallible

* fix flaky test

not needed anymore since JWTs now uniquely identify the module

* also, add `rust-toolchain.toml`