Generate actual JWTs for signing

[ltitanb]

Currently we just pass the raw jwt secret in the headers

commit-boost-client/crates/signer/src/service.rs

Lines 98 to 114 in 07d03fd

	async fn jwt_auth(
	State(state): State<SigningState>,
	TypedHeader(auth): TypedHeader<Authorization<Bearer>>,
	mut req: Request,
	next: Next,
	) -> Result<Response, SignerModuleError> {
	let jwt: Jwt = auth.token().to_string().into();
	let module_id = state.jwts.get_by_right(&jwt).ok_or_else(|| {
	error!("Unauthorized request. Was the module started correctly?");
	SignerModuleError::Unauthorized
	})?;
	req.extensions_mut().insert(module_id.clone());
	Ok(next.run(req).await)
	}

but we should instead generate / verify actual jwts eg via https://crates.io/crates/jsonwebtoken

ref: https://self-issued.info/docs/draft-jones-json-web-token-01.html