feat(op): allow scope without openid

This changes removes the requirement of the openid scope to be set for all token requests.
As this library also support OAuth2-only authentication mechanisms we still want to sanitize requested scopes, but not enforce the openid scope.

Related to https://github.com/zitadel/zitadel/discussions/8068

pkg/op/auth_request_test.go

@@ -137,11 +137,6 @@ func TestValidateAuthRequest(t *testing.T) {
 			args{&oidc.AuthRequest{}, mock.NewMockStorageExpectValidClientID(t), nil},
 			oidc.ErrInvalidRequest(),
 		},
-		{
-			"scope openid missing fails",
-			args{&oidc.AuthRequest{Scopes: []string{"profile"}}, mock.NewMockStorageExpectValidClientID(t), nil},
-			oidc.ErrInvalidScope(),
-		},
 		{
 			"response_type missing fails",
 			args{&oidc.AuthRequest{Scopes: []string{"openid"}}, mock.NewMockStorageExpectValidClientID(t), nil},
@@ -287,16 +282,6 @@ func TestValidateAuthReqScopes(t *testing.T) {
 				err: true,
 			},
 		},
-		{
-			"scope openid missing fails",
-			args{
-				mock.NewClientExpectAny(t, op.ApplicationTypeWeb),
-				[]string{"email"},
-			},
-			res{
-				err: true,
-			},
-		},
 		{
 			"scope ok",
 			args{