Open dataset

[annakrystalli]

This PR can be installed with:

remotes::install_github("Infectious-Disease-Modeling-Hubs/hubUtils",
                       dependencies = TRUE, ref = "open-dataset")

• Implements approach to loading forecasts discussed in Define `load_forecasts` approach & scope #44 using function connect_hub()
• Also allows for connection to hubs in AWS S3 buckets and soon to support Google Storage buckets.
• Resolves Explore using arrow datasets for accessing hub model outputs #37
• Resolves Create hub connection S3 class #2
• Resolves validate_hub_connection() A validator that will perform checks to ensure that the object has correct values #5
• Supports connecting to infomal hubs through separate function connect_model_output(). Resolves support operations on informal hubs #35
• Currently does not facilitate Evaluate the need for accommodating multiple model output file formats in a single hub #40 . Will monitor in arrow repository for potential to implement.
• Also includes minor fixes and improvements to view_config_val_errors() and validate_config() and fixes failing view_config_val_errors() snapshot tests.