SE-1970 Fix sandbox provisioning failure due to prospectus

Description

Currently, the sandbox provisioning from master branch fails at [this ansible task](https://github.com/edx/configuration/blob/master/playbooks/roles/nginx/tasks/main.yml#L278-L288) due to prospectus preview variables `PROSPECTUS_PREVIEW_HTPASSWD_USER` and `PROSPECTUS_PREVIEW_HTPASSWD_PASS`, not being defined by default.

This PR adds a default value to these variables which can be overridden if needed.

*JIRA tickets:* TBD

*Dependencies:* None

*Merge deadline:* ASAP - this is breaking provisioning that was previously working

*Reviewers*:

  • [ ] @xitij2000

  • [ ] edX reviewer[s] TBD

Assignee

Unassigned

Reporter

Open Source Pull Request Bot

Labels

Contributor Name

Pooja Kulkarni

Repo

edx/configuration

Customer

Epic Link

None

OSCM Assignee

None

Platform Map Area (Levels 1 & 2)

Developer Experiences

Platform Map Area (Levels 3 & 4)

None

Blended Hour Utilization Percentage

None

Priority

Unset
Configure