[Issue 2665] Update analytics db settings to recognize empty pwd sett…

…ing in env (#2796)

## Summary
Fixes #2665

### Time to review: __1 min__

## Changes proposed
> What was added, updated, or removed in this PR.

Made `DBSettings.password` an optional field in `analytics/config.py`,
thereby allowing the value to be `None`, which in turn allows IAM
token-creation to occur.

## Context for reviewers
> Testing instructions, background context, more in-depth details of the
implementation, and anything else you'd like to call out or ask
reviewers. Explain how the changes were verified.

## Additional information
> Screenshots, GIF demos, code examples or output to help show the
changes working as expected.

analytics/config.py

@@ -14,8 +14,8 @@ class DBSettings(PydanticBaseEnvConfig):
      db_host: str = Field(alias="DB_HOST")
      port: int = Field(5432,alias="DB_PORT")
      user: str = Field (alias="DB_USER")
-     password: str = Field(alias="DB_PASSWORD")
-     ssl_mode: str = Field(alias="DB_SSL_MODE")
+     password: Optional[str] = Field(None, alias="DB_PASSWORD")
+     ssl_mode: str = Field("require", alias="DB_SSL_MODE")
      slack_bot_token: str = Field(alias="ANALYTICS_SLACK_BOT_TOKEN")
      reporting_channel_id: str = Field(alias="ANALYTICS_REPORTING_CHANNEL_ID")
      aws_region: Optional[str] = Field(None, alias="AWS_REGION")