Add connect OAuth metadata and update OIDC handlers

Expose per-portal OAuth client metadata from connect and route OIDC
authorization through compliance portal session state.

Signed-off-by: Bryan Frimin <bryan@probo.com>

pkg/server/api/connect/v1/oauth2_metadata_test.go

@@ -0,0 +1,45 @@
+// Copyright (c) 2026 Probo Inc <hello@probo.com>.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+package connect_v1_test
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"go.probo.inc/probo/pkg/baseurl"
+	"go.probo.inc/probo/pkg/coredata"
+	connect_v1 "go.probo.inc/probo/pkg/server/api/connect/v1"
+	"go.probo.inc/probo/pkg/uri"
+)
+
+func TestOAuth2ServerMetadata(t *testing.T) {
+	t.Parallel()
+
+	baseURL := baseurl.MustParse("https://auth.example.com")
+	metadata := connect_v1.OAuth2ServerMetadata(baseURL, nil)
+
+	assert.Equal(t, uri.URI("https://auth.example.com"), metadata.Issuer)
+	assert.Equal(
+		t,
+		uri.URI("https://auth.example.com/api/connect/v1/oauth2/authorize"),
+		metadata.AuthorizationEndpoint,
+	)
+	assert.Equal(
+		t,
+		uri.URI("https://auth.example.com/api/connect/v1/oauth2/token"),
+		metadata.TokenEndpoint,
+	)
+	assert.Contains(t, metadata.ScopesSupported, coredata.OAuth2Scope("openid"))
+}