feat(NODE-3920)!: validate options are not repeated in connection string

[nbbeeken]

Description

What is changing?

• Add validation for repeated options that aren't readPreferenceTags
• Fix bug with empty readPreferenceTags

Is there new documentation needed for these changes?

None

What is the motivation for this change?

See highlights

Release Highlight

Repeated options in connection string are no longer allowed

In order to avoid accidental misconfiguration the driver will no longer prioritize the first instance of an option provided on the URI. Instead repeated options that are not permitted to be repeated will throw an error. This is to that connection strings that contain options like tls=true&tls=false are no longer ambiguous.

Empty readPreferenceTags in connection string fixed

The following connection string will now produce the following readPreferenceTags:

"mongodb://host?readPreferenceTags=region:ny&readPreferenceTags=rack:r1&readPreferenceTags=";
// client.options.readPreference.tags
[{ region: 'ny' }, { rack: 'r1' }, { }];

The empty readPreferenceTags allows drivers to still select a server if the leading tag conditions are not met.

Double check the following

• Ran npm run check:lint script
• Self-review completed using the steps outlined here
• PR title follows the correct format: type(NODE-xxxx)[!]: description
  • Example: feat(NODE-1234)!: rewriting everything in coffeescript
• Changes are covered by tests
• New TODOs have a related JIRA ticket