Adding solr cloud service to babel

[liseli]

This PR is to integrate Solr 8 in the babel repository, with these changes we are ready to apply changes on ls and test them by accessing the Solr 8 cluster.

You will start up the services following the instructions in the README.md file.

Once Solr is up and running, access http://localhost:8981/solr/#/~cloud?view=graph, and you will see

The Solr cluster will start and create the collection, but we must manually index the sample data to run queries on the front end. I've created the ticket ETT-1678 to generate an image with the sample data, and then we can add these services to the Docker environment to automatically start Solr with data for testing.

Meanwhile, the process for indexing data is explained here. I've tested it, and it works, but you will need to clone the lss_solr_configs repository to your machine and follow the steps to run the script indexing_data.sh.

After indexing the sample data, you will run queries and see the results

[eumalin]

Not sure if depends_on: zoo1 is actually doing anything once it goes through extends: in the main compose file (Compose doesn't carry depends_on through extends, it has to be redeclared where you extend it). Does zoo1 come up before solr?

[moseshll]

In Solr Admin/ZK Status I get the warning

Could not execute ruok towards ZK host zoo1:2181. Add this line to the 'zoo.cfg' configuration file on each zookeeper node: '4lw.commands.whitelist=mntr,conf,ruok'. See also chapter 'Setting Up an External ZooKeeper Ensemble' in the Solr Reference Guide.

Not sure if this is expected.

Also, after performing the steps outlined in lss_solr_configs, core-x_shard1_replica_n1 shows 0 documents. Maybe its the ZK status thing. I guess it doesn't matter since one of the next steps is to have a sample index integrated so we don't have to do this manually.