Allow to validate provider metadata

According to the OpenID Connect Discovery 1.0 spec.
Provide the default values for fields when they are defined.
Introduce VerifiedProviderMetadata.
Rename Metadata to ProviderMetadata.
Implement Deserialize for ProviderMetadata.

Cargo.lock

@@ -123,6 +123,12 @@ dependencies = [
  "password-hash",
 ]
 
+[[package]]
+name = "assert_matches"
+version = "1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9b34d609dfbaf33d6889b2b7106d3ca345eacad44200913df5ba02bfd31d2ba9"
+
 [[package]]
 name = "async-compression"
 version = "0.3.14"
@@ -2803,6 +2809,7 @@ dependencies = [
 name = "oauth2-types"
 version = "0.1.0"
 dependencies = [
+ "assert_matches",
  "chrono",
  "data-encoding",
  "http",

clippy.toml

@@ -1 +1,2 @@
 msrv = "1.60.0"
+doc-valid-idents = ["OpenID", "OAuth", ".."]

crates/handlers/src/oauth2/discovery.rs

@@ -25,7 +25,7 @@ use mas_iana::{
 use mas_jose::{SigningKeystore, StaticKeystore};
 use mas_router::UrlBuilder;
 use oauth2_types::{
-    oidc::{ClaimType, Metadata, SubjectType},
+    oidc::{ClaimType, ProviderMetadata, SubjectType},
     requests::{Display, GrantType, Prompt, ResponseMode},
     scope,
 };
@@ -134,7 +134,7 @@ pub(crate) async fn get(
 
     let prompt_values_supported = Some(vec![Prompt::None, Prompt::Login, Prompt::Create]);
 
-    let metadata = Metadata {
+    let metadata = ProviderMetadata {
         issuer,
         authorization_endpoint,
         token_endpoint,
@@ -161,7 +161,7 @@ pub(crate) async fn get(
         request_parameter_supported,
         request_uri_parameter_supported,
         prompt_values_supported,
-        ..Metadata::default()
+        ..ProviderMetadata::default()
     };
 
     Json(metadata)

crates/oauth2-types/Cargo.toml

@@ -22,3 +22,6 @@ itertools = "0.10.3"
 
 mas-iana = { path = "../iana" }
 mas-jose = { path = "../jose" }
+
+[dev-dependencies]
+assert_matches = "1.5.0"