Feat: cache public key

[oddgrd]

No description provided.

[chesedo]

This is great! I think we can make this even simpler by implementing the cache in this function. Then we don't have to pass around a cache manager since we can initiate the cache inside AuthPublicKey::new()

shuttle/common/src/backends/auth.rs

Lines 286 to 292 in 6686657

	async fn public_key(&self) -> Result<Vec<u8>, Self::Error> {
	let client = Client::new();
	let uri = format!("{}public-key", self.auth_uri).parse()?;
	let res = client.get(uri).await?;
	let buf = body::to_bytes(res).await?;
	Ok(buf.to_vec())
	}

[chesedo]

LGTM