RedisDsn doesn't support password

[hardbyte]

Checks

• I added a descriptive title to this issue
• I have searched (google, github) for similar issues and couldn't find anything
• I have read and followed the docs and still think this is a bug

Bug

Ref #1275

Output of python -c "import pydantic.utils; print(pydantic.utils.version_info())":

             pydantic version: 1.7.3
            pydantic compiled: True
                 install path: /home/brian/.cache/pypoetry/virtualenvs/j7nrLfcR-py3.8/lib/python3.8/site-packages/pydantic
               python version: 3.8.5 (default, Jul 28 2020, 12:59:40)  [GCC 9.3.0]
                     platform: Linux-5.4.0-65-generic-x86_64-with-glibc2.29
     optional deps. installed: ['typing-extensions', 'email-validator']

Redis can be configured to require a password but not a user. The pydantic RedisDsn doesn't support this, and can't seem to be tricked by passing user as an empty string or None:

>>> from pydantic import RedisDsn
>>> RedisDsn.build(scheme='redis', user='', password="testpass", host="host", path='')
'redis://host'
>>> RedisDsn.build(scheme='redis', user=None, password="testpass", host="host", path='')
'redis://host'
>>> RedisDsn.build(scheme='redis', password="testpass", host="host", path='')
'redis://host'

Expected behaviour:

>>> from pydantic import RedisDsn
>>> RedisDsn.build(scheme='redis', user='', password="testpass", host="host", path='')
'redis://:testpass@host'

[PrettyWood]

Hi @hardbyte
The exact same issue has been opened this morning and answered ;)
Hope it helps!

[hardbyte]

Thanks!