Feature/#174 add mongodb support

[WahiduzzamanKhan]

Closes #174

Changes description

• Added support for MongoDB as a data storage backend (see data-storage-mongodb.R)
• Added example app for MongoDB
• Created automated tests for DataStorageMongoDB class

Definition of done

• Have you read the Contributing Guidelines?
• NEWS.md file has been updated
• Development version has been bumped (x.y.z.90XX)
• Issue has been linked with this PR (via Closing keywords or right sidebar under Development)

[averissimo]

It's a good boilerplate code for Mongo, but this PR is not ready for merge. It has a bunch of issues described below.

I'll be fixing them on a separate PR and merge against this one :-)

Non-exaustive list:

• Documentation
  • With references to MariaDB
  • Parameters for constructor are incorrect (using inexisting parameter called url)
  • Examples are failing
• Functionality
  • Read doesn't work if only integers were written
  • Read doesn't work for sequential arrays (returns "1:10" string instead of [1,2,3,4,5,6,7,8,9])
• Automated tests fail
  • When setting up docker container and running
  • Collection paramaeter

Sys.setenv(
    TEST_MONGODB_USER = "root",
    TEST_MONGODB_PASSWORD = "example",
    TEST_MONGODB_HOSTNAME = "localhost",
    TEST_MONGODB_PORT = 27017,
    
    TEST_MONGODB_DBNAME = "shiny_telemetry",
    TEST_MONGODB_COLLECTION = "event_log"
)
devtools::test()