Create buckets with custom retention policies

From community:
https://community.influxdata.com/t/influxdb2-x-bucket-retention-feature-request/25546

**Proposal:**
The ability to create a bucket with a custom retention policy (a value outside of the dropdown options)


**Current behavior:**
You must select a retention policy duration from the dropdown list when creating a bucket.

**Desired behavior:**
Create a bucket with a user input retention policy.

**Use case:**
Users aren't required to install and configure the CLI to make a bucket with a custom retention policy.

Thank you!