Updating customer fails when NativeAuthenticationMethod not configured

[michaelbromley]

Describe the bug
A change in v1.2.1 in response to #1071 prevents updating customers if the NativeAuthenticationMethod is not being used (e.g. when relying solely on an external auth method).

This is because when updating the Customer, if the emailAddress input is present (as is always the case when using the Admin UI), then this method gets called:

vendure/packages/core/src/service/services/user.service.ts

Lines 208 to 222 in 1ebc872

	async changeNativeIdentifier(ctx: RequestContext, userId: ID, newIdentifier: string) {
	const user = await this.getUserById(ctx, userId);
	if (!user) {
	return;
	}
	const nativeAuthMethod = user.getNativeAuthenticationMethod();
	user.identifier = newIdentifier;
	nativeAuthMethod.identifier = newIdentifier;
	nativeAuthMethod.identifierChangeToken = null;
	nativeAuthMethod.pendingIdentifier = null;
	await this.connection
	.getRepository(ctx, NativeAuthenticationMethod)
	.save(nativeAuthMethod, { reload: false });
	await this.connection.getRepository(ctx, User).save(user, { reload: false });
	}

The user.getNativeAuthenticationMethod(); call will throw an error if it is not found.

The solution is:

1. Only invoke that changeNativeIdentifier() method if the email address has changed
2. Inside the method, use a try-catch block to prevent errors if it ever gets called in a situation with no native auth configured.

Environment (please complete the following information):

• @vendure/core version: 1.2.1