DOP-3998: allow preprd to use URL for search staging server

[seungpark]

PR description:

• this PR allows autobuilder to pipe in a front end variable GATSBY_MARIAN_URL to let the client side know which search server to point to.
• AWS parameter store values have been stored, with stg environment pointing to stage search url https://docs-search-transport.docs.staging.corp.mongodb.com/

PREREQ prs
search transport server must allow CORS authentication
front end must supply credentials when making requests to authenticate through corpsecure

Sample of change
Staged site, making requests to staging search server (will have to be authenticated in same browser for search staging to send credentials)

generate authentication token by visiting https://docs-search-transport.docs.staging.corp.mongodb.com/v2/status

shows request being made to staging search server:

[github-actions]

The URL for your feature branch webhook is https://tp4nq09sc3.execute-api.us-east-2.amazonaws.com/prod/

[mmeigs]

Looks good! Only thing is that I believe preprd is actually dotcomstg not stg. stg is content writers staging.

[seungpark]

Looks good! Only thing is that I believe preprd is actually dotcomstg not stg. stg is content writers staging.

yes! i updated both the param store values for dotcomstg and stg (stg was for testing purposes!) should see the changes when we deploy docs-qa as well 👍