DEV-517: Bump Puma, support setting min threads

- Bumps Puma to ≥v6.4 to improve performance.
  Among other changes, Puma will now tend to
  route requests to worker with lower load.
- Supports setting min/max threads independently.
  We previously did this a la Heroku, which sets
  them to the same value, but that doesn't make
  as much sense in Berkeley's environments due to
  it helping us to conserve resources when load
  is low.

.gitignore

@@ -74,12 +74,4 @@ yarn-debug.log*
 /artifacts/
 
 # Ignore solr files
-/solr/geodata-test/data/index/*
-/solr/geodata-test/data/tlog/*
-/solr/geodata/data/index/*
-/solr/geodata/data/tlog/*
-
-!/solr/geodata-test/data/index/.keep
-!/solr/geodata-test/data/tlog/.keep
-!/solr/geodata/data/index/.keep
-!/solr/geodata/data/tlog/.keep
+solr/*/data/*

Gemfile

@@ -15,7 +15,7 @@ gem 'jbuilder'
 gem 'jquery-rails'
 gem 'omniauth-cas'
 gem 'pg', '~> 1.4.6'
-gem 'puma', '~> 5.0'
+gem 'puma', '~> 6.4.1'
 gem 'rack-timeout', '~> 0.6.3'
 gem 'rails', '~> 7.0.8'
 gem 'rsolr', '>= 1.0', '< 3'