```output
cargo update
    Updating crates.io index
     Locking 27 packages to latest compatible versions
    Updating anyhow v1.0.88 -> v1.0.89
    Updating arrayref v0.3.8 -> v0.3.9
    Updating aws-lc-sys v0.21.1 -> v0.21.2
    Updating axum v0.7.5 -> v0.7.6
    Updating axum-core v0.4.3 -> v0.4.4
    Updating bytes v1.7.1 -> v1.7.2
    Updating casbin v2.4.0 -> v2.5.0
    Updating cc v1.1.18 -> v1.1.21
    Updating clap v4.5.17 -> v4.5.18
    Updating clap_builder v4.5.17 -> v4.5.18
    Updating clap_derive v4.5.13 -> v4.5.18
    Updating iana-time-zone v0.1.60 -> v0.1.61
    Updating lettre v0.11.8 -> v0.11.9
    Updating pest v2.7.12 -> v2.7.13
    Updating pest_derive v2.7.12 -> v2.7.13
    Updating pest_generator v2.7.12 -> v2.7.13
    Updating pest_meta v2.7.12 -> v2.7.13
    Updating pkg-config v0.3.30 -> v0.3.31
    Updating security-framework-sys v2.11.1 -> v2.12.0
    Updating thiserror v1.0.63 -> v1.0.64
    Updating thiserror-impl v1.0.63 -> v1.0.64
    Updating toml_edit v0.22.20 -> v0.22.21
      Adding tower v0.5.1
    Updating tower-http v0.5.2 -> v0.6.1
    Updating unicode-normalization v0.1.23 -> v0.1.24
    Updating unicode-script v0.5.6 -> v0.5.7
    Updating webpki-roots v0.26.5 -> v0.26.6
```

Mutable static variables are discouraged. I guess we should move them to
the proxy service. We wanted to avoid generating the error images every
time we need them becuase it's costly. I would created them when the
proxy service is instanciated or maybe we can create a new service with
static content for the proxy.