fix: "SCRAM-SHA-1 requires a username" error for mongodb srv config with username

[kaustavb12]

Description

Currently we are setting None to mongodb username and password parameters in FORUM_MONGODB_CLIENT_PARAMETERS.

PyMongo currently throws the following error if the credentials as added to the host parameter as a connection string.

pymongo.errors.ConfigurationError: SCRAM-SHA-1 requires a username.

This PR fixes this issue by omitting the two parameters completely if the corresponding values are not available.

Other information

Private Ref : BB-9353

[0x29a]

LGTM 👍

[regisb]

I'm not sure I understand. What is the value of FORUM_MONGODB_CLIENT_PARAMETERS for you? Is the LMS container crashing?

Also, please add a changelog entry: https://docs.tutor.edly.io/tutor.html#contributing Make sure to describe why you are doing this change, and not what change you are doing. E.g: do not say "set variable to None" but "fix crashing LMS container when setting FORUM_XYZ parameter".

[kaustavb12]

@regisb Changelog entry added.

Here's the value of FORUM_MONGODB_CLIENT_PARAMETERS in LMS settings without this change:

FORUM_MONGODB_CLIENT_PARAMETERS = {
    "host": "mongodb+srv://username:password@mongo.db.hostname",
    "port": 27017,
    "username": None,
    "password": None,
    "ssl": True,
}

This crashes this LMS init job (specifically, the forum_create_mongodb_indexes management command invoked in that job fails) with the exception

pymongo.errors.ConfigurationError: SCRAM-SHA-1 requires a username

With the changes from this PR, the value of FORUM_MONGODB_CLIENT_PARAMETERS becomes:

FORUM_MONGODB_CLIENT_PARAMETERS = {
    "host": "mongodb+srv://username:password@mongo.db.hostname",
    "port": 27017,
    "ssl": True,
}

This works correctly.

[regisb]

Awesome, thanks!