Minimum supported rustls version is 0.21.4 not 0.21.0

[MathiasPius]

Current and expected behavior

Building kube-client using the minimal crate versions as specified in Cargo.toml fails.

Reproduction, in kube-client 0.87.1 or crate that relies on it:

$ cargo +nightly update -Zminimal-versions
$ cargo build

Results in:

error[E0599]: no method named `with_client_auth_cert` found for struct `ConfigBuilder` in the current scope
  --> /home/mpd/.cargo/registry/src/index.crates.io-6f17d22bba15001f/kube-client-0.87.1/src/client/tls.rs:56:18
   |
55 | /             config_builder
56 | |                 .with_client_auth_cert(chain, pkey)
   | |                 -^^^^^^^^^^^^^^^^^^^^^ help: there is a method with a similar name: `with_no_client_auth`
   | |_________________|
   | 

Method with_client_auth_cert was only renamed from with_single_cert in rustls 0.21.4 meaning versions prior to 0.21.4 are incompatible with kube-client.

Possible solution

Update minimum rustls dependency in kube-client's Cargo.toml to 0.21.4.

Additional context

kube-client calls rustls::client::builder::ConfigBuilder::.with_client_auth_cert which was named with_single_cert prior to rustls version v0.21.4, making kube-client incompatible with rustls versions <v0.21.4.

Environment

Irrelevant

Configuration and features

No response

Affected crates

kube-client

Would you like to work on fixing this bug?

yes