When creating a new account, an invalid username occupy an email address

Description:

When creating a new account, if the user types in an invalid username(in my case I have a space in between), the email(which is prompted before username) will be reserved hence it can not be used even after the user modifies the username.

I confirmed this bug by using this unit test in testing mode(follow the steps in https://developer.rocket.chat/contribute-to-rocket.chat/modes-of-contribution/assist-with-testing-rocket.chat)

it('should send email to user (return success), when is a valid email', (done) => {
			request
				.post(api('users.sendConfirmationEmail'))
				.set(credentials)
				.send({
					email: adminEmail,
				})
				.expect('Content-Type', 'application/json')
				.expect(200)
				.expect((res) => {
					expect(res.body).to.have.property('success', true);
				})
				.end(done);
		});

I first replaced the adminEmail with an email that is not valid(not existed) and this test failed. Then I tried to create an account using an invalid username(with space in between) with the same email. I clicked the "Join your team" button once and there was no response. I clicked the button once again and it prompted that the email is already existed. I ran the unit test above again and it passed which means the email is written to the database.

In the actual server, the same behavior holds.

Testing Server:
https://github.com/RocketChat/Rocket.Chat/assets/62249815/75b0d5b4-7864-4910-a975-8647dd1f3056

Actual Server:

https://github.com/RocketChat/Rocket.Chat/assets/62249815/90a3cd35-b873-4219-8214-3bc3510054b8

Steps to reproduce:

1. Follow my procedures above.

Expected behavior:

Should not reserve the email and prompt the username is invalid.

Actual behavior:

The email is reserved and not telling the username is invalid.

Server Setup Information:

• Version of Rocket.Chat Server: 6.5.0-develop
• Operating System: macOS 13.4.1 (22F82)
• Deployment Method:
• Number of Running Instances: 1
• DB Replicaset Oplog: Enabled
• NodeJS Version: 14.21.4 - x64
• MongoDB Version: 6.0.3

Client Setup Information

• Desktop App or Browser Version:
• Operating System:

Additional context

Relevant logs:

Start with the users.sendConfirmationEmail unit test and the account-creation flow described in the report, then reproduce the invalid-username case in testing mode. Trace when the email is persisted after username validation; done means an invalid username is reported without reserving the email, while the valid-email confirmation test still passes.