[Localization improvements] MongoDB translation storage changes

[pdcp1]

This issue is part of the epic #3268

Improvements

1. Change the way we store the translations. Using just one reports collection with a new document field language.

• Collections that will be removed:
  • translations/reports_en
  • translations/reports_es
  • translations/reports_fr
  • translations/reports_ja
• Collection that will be added
  • translations/reports
• About the new translations/reports collection
  • The collection will include translations of all reports in the system.
  • A new document field named language will be introduced to identify the translation language.

3. Change the API to use this new DB approach
4. Change the client graphql mutations to use the language code as a parameter

PR

• Refactor translation reports collection and Gatsby source plugin #3290