fix: Removes nullable from DBUser password

[cveticm]

Proposed changes

Fixes #556

On Gemini CLI, tool atlas-create-dbusers would be skipped due to missing types in paramter schema.
This seems to be caused by setting password as both optional and nullable.
I have replaced this with nullish (both optional and nullable).
This resolves the issue.

before fix:

after fix:

Checklist

• I have signed the MongoDB CLA

[Copilot]

Pull Request Overview

Fixes an issue where the atlas-create-dbusers tool was being skipped due to missing types in parameter schema by replacing separate .optional() and .nullable() chaining with the combined .nullish() method for the password field.

• Replaces chained .optional().nullable() with .nullish() for the password field in DBUser creation schema
• Resolves parameter schema validation issues that prevented the tool from being recognized by Gemini CLI

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[himanshusinghs]

Good catch 🚀 @nirinchev should we pull this for 1.0.0?

[nirinchev]

Can we test the impact of this change with several agents - notably, we want to ensure the agent doesn't generate a password unless explicitly prompted for it. Otherwise, happy to pull it in.

[cveticm]

Can we test the impact of this change with several agents - notably, we want to ensure the agent doesn't generate a password unless explicitly prompted for it. Otherwise, happy to pull it in.

@nirinchev Tested with copilot agents GPT, grok, Claude and gemini. All exclude password or provide null value if not explicitly prompted to include password. Additionally, user provided password is used when prompted. ie, behaviour remains the same.
Let me know if there is additional agents you'd like me to test with

[gagik]

Tested with copilot agents GPT, grok, Claude and gemini

If this was only in VSCode/Copilot might also be worth verifying in a different agent (i.e. Claude Desktop or Cursor) and not model just to make sure they interpret JSON schema correctly as well