Add authentication from upstream providers (#107)

Let BasicOIDC delegate authentication to upstream providers (Google, GitHub, GitLab, Keycloak...)

Reviewed-on: #107

src/data/jwt_signer.rs

@@ -11,8 +11,10 @@ use base64::Engine as _;
 use crate::utils::err::Res;
 use crate::utils::string_utils::rand_str;
 
+const JWK_USE_SIGN: &str = "sig";
+
 /// Json Web Key <https://datatracker.ietf.org/doc/html/rfc7517>
-#[derive(serde::Serialize, serde::Deserialize)]
+#[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
 pub struct JsonWebKey {
     #[serde(rename = "alg")]
     algorithm: String,
@@ -24,6 +26,8 @@ pub struct JsonWebKey {
     modulus: String,
     #[serde(rename = "e")]
     public_exponent: String,
+    #[serde(rename = "use", skip_serializing_if = "Option::is_none")]
+    usage: Option<String>,
 }
 
 #[derive(Debug, Clone)]
@@ -44,6 +48,7 @@ impl JWTSigner {
             key_id: self.0.key_id().as_ref().unwrap().to_string(),
             public_exponent: BASE64_URL_URL_SAFE.encode(components.e),
             modulus: BASE64_URL_SAFE_NO_PAD.encode(components.n),
+            usage: Some(JWK_USE_SIGN.to_string()),
         }
     }