Allow empty password in basicauth

[tevino]

1. What does this change do, exactly?

Allow empty password in basicauth

2. Please link to the relevant issues.

There isn't, but here is a TODO.

3. Which documentation changes (if any) need to be made because of this PR?

Maybe an empty password example could be added into the example in README.md, but I'm not sure if it is a good idea to encourage people to set empty passwords.

4. Checklist

• [x] I have written tests and verified that they fail without my change
• [x] I made pull request as minimal and simple as possible. If change is not small or additional dependencies are required, I opened an issue to propose and discuss the design first
• [x] I have squashed any insignificant commits
• [ ] This change has comments for package types, values, functions, and non-obvious lines of code