fix(auth): repair the inert auth configuration schema

The schema string was the inside of a "properties" block: jwts, oidc, ldap and
required sat at the root with no enclosing "type"/"properties". jsonschema
compiled it as a document with only unknown keywords, so every auth section
validated and no option was ever checked.

Wrapped it correctly and dropped the root-level required: ["jwts"]. Init logs
and continues when the jwts section is absent ("Missing JWT configuration: No
JWT token support!"), so enforcing it would abort OIDC- or LDAP-only
deployments that work today. The per-subsection required lists are unchanged.

Validation errors are now printed with err.Error() instead of %#v, which
rendered a jsonschema.ValidationError unreadably.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

internal/auth/schema_test.go

@@ -0,0 +1,104 @@
+// Copyright (C) NHR@FAU, University Erlangen-Nuremberg.
+// All rights reserved. This file is part of cc-backend.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package auth
+
+import (
+	"encoding/json"
+	"os"
+	"testing"
+
+	"github.com/santhosh-tekuri/jsonschema/v5"
+)
+
+// compileConfigSchema guards against the schema silently degrading into a
+// document with no constraints (which is what happens when the "type"/
+// "properties" wrapper is missing: every instance validates).
+func compileConfigSchema(t *testing.T) *jsonschema.Schema {
+	t.Helper()
+	sch, err := jsonschema.CompileString("schema.json", configSchema)
+	if err != nil {
+		t.Fatalf("compiling auth config schema: %v", err)
+	}
+	return sch
+}
+
+func validateAuthConfig(t *testing.T, sch *jsonschema.Schema, raw string) error {
+	t.Helper()
+	var v any
+	if err := json.Unmarshal([]byte(raw), &v); err != nil {
+		t.Fatalf("invalid test json: %v", err)
+	}
+	return sch.Validate(v)
+}
+
+func TestConfigSchemaAccepts(t *testing.T) {
+	sch := compileConfigSchema(t)
+
+	tests := map[string]string{
+		"jwts only":    `{"jwts":{"max-age":"2000h"}}`,
+		"oidc only":    `{"oidc":{"provider":"http://localhost:8080/realms/cc"}}`,
+		"empty":        `{}`,
+		"ldap":         `{"ldap":{"url":"ldap://127.0.0.1:389","user-base":"ou=users,dc=example,dc=com","search-dn":"cn=admin,dc=example,dc=com","user-bind":"uid={username},ou=users,dc=example,dc=com","user-filter":"(objectclass=posixAccount)","role-filters":{"admin":"(memberOf=cn=cc-admin,ou=groups,dc=example,dc=com)"}}}`,
+		"role-mapping": `{"oidc":{"provider":"http://p","role-mapping":{"cc-admin":"admin"}}}`,
+	}
+
+	for name, raw := range tests {
+		if err := validateAuthConfig(t, sch, raw); err != nil {
+			t.Errorf("%s: unexpected validation error: %v", name, err)
+		}
+	}
+}
+
+func TestConfigSchemaRejects(t *testing.T) {
+	sch := compileConfigSchema(t)
+
+	tests := map[string]string{
+		"jwts without max-age":      `{"jwts":{"public-key":"abc"}}`,
+		"jwts max-age not a string": `{"jwts":{"max-age":2000}}`,
+		"oidc without provider":     `{"oidc":{"client-id":"cc-backend"}}`,
+		"ldap without user-bind":    `{"ldap":{"url":"ldap://127.0.0.1:389","user-base":"ou=users","search-dn":"cn=admin","user-filter":"(objectclass=posixAccount)"}}`,
+		"role-filters not strings":  `{"ldap":{"url":"u","user-base":"b","search-dn":"d","user-bind":"ub","user-filter":"f","role-filters":{"admin":true}}}`,
+		"jwts not an object":        `{"jwts":"2000h"}`,
+	}
+
+	for name, raw := range tests {
+		if err := validateAuthConfig(t, sch, raw); err == nil {
+			t.Errorf("%s: expected validation error, got none", name)
+		}
+	}
+}
+
+// TestConfigSchemaExampleConfigs validates the auth sections of the shipped
+// example configurations.
+func TestConfigSchemaExampleConfigs(t *testing.T) {
+	sch := compileConfigSchema(t)
+
+	for _, path := range []string{
+		"../../configs/config.json",
+		"../../configs/config-demo.json",
+		"../../configs/config-large.json",
+	} {
+		raw, err := os.ReadFile(path)
+		if err != nil {
+			t.Fatal(err)
+		}
+		var sections map[string]json.RawMessage
+		if err := json.Unmarshal(raw, &sections); err != nil {
+			t.Fatal(err)
+		}
+		authCfg, ok := sections["auth"]
+		if !ok {
+			continue
+		}
+		var v any
+		if err := json.Unmarshal(authCfg, &v); err != nil {
+			t.Fatal(err)
+		}
+		if err := sch.Validate(v); err != nil {
+			t.Errorf("%s: auth section does not validate: %v", path, err)
+		}
+	}
+}