Enable alloc feature for base64 dependency

[dvzrv]

Hi! 👋

I'm using this crate in the context of nethsm.
I noticed that I am no longer able to upgrade my lock file as this leads to clippy failing:

    Checking nethsm-sdk-rs v1.0.0
error[E0599]: no method named `encode` found for struct `GeneralPurpose` in the current scope
   --> /home/dave/.local/state/cargo/registry/src/index.crates.io-6f17d22bba15001f/nethsm-sdk-rs-1.0.0/src/apis/mod.rs:122:51
    |
122 |     format!("Basic {}", general_purpose::STANDARD.encode(string)).to_string()
    |                                                   ^^^^^^ method not found in `GeneralPurpose`

This appears to be broken if base64 >=0.22.0 is pulled in by another dependency in the tree.

Do you have a timeline for updating/ adapting this crate (its last release is from six months ago)?

[robin-nitrokey]

The cause for this problem is that we do not enable the alloc feature for base64 in our Cargo.toml. Probably some dependency does, but when it updates base64 to an incompatible version, the feature is no longer enabled for our version.

You should be able to temporarily fix this on your side by manually pulling in base64 and activating the feature:

[dependencies]
base64 = { version = "0.21", default-features = false, features = ["alloc"] }