Refactor `meilisearch.rb`

[ellnix]

• [ ] Streamline interface
  • [ ] remove similarly named instance and class methods where one often just calls the other
  • [ ] reduce method side effects
  • [ ] reduce hacks in methods
  • [ ] clarify bang method API
  • [ ] do not use flag parameters (i. e. product.index!(true))
  • [ ] make return types more consistent
• [ ] Reach 95%+ code coverage
• [ ] More robust error reporting (no failing silently)
• [ ] Break meilisearch.rb into multiple files/modules
• [ ] Add a system for validating configurations