Restore cross-searching

[ignasi35]

Starting sometime around mid-september 2020, the search box in lagomframework.com stopped returning results. Inspecting with the JS console on the browser pointed to a 403 status response from the Algolia servers.

The temporary fix in #232 disables cross-search (searching across multiple algolia indices) under the assumption that Algolia implemented more restrictive permissions. The problem is that Akka, Play and Lagom websites are indexed separately by Algolia and each of the sites uses different credentials to query the indices. So, the cross-search implementation in lagomframework.com would send multiple search queries to gather results from all three indices at once. Each query was supposedly built and run using the correct credentials for each index. Apparently only the lagom credentials were being used.

I suspect that in order to restore cross-searching the implementation needs to clearly separate any query to Algolia to use a single index on each request. This will require some rework on our end in order to gather and reorder results depending on what index the results were found on.

Refs https://discuss.lightbend.com/t/documentation-search-does-not-work/7249