Add diseasystore for ECDC respitory viruses data

[RasmusSkytte]

Intent

This PR introduces a diseasystore for the ECDC Respiratory Viruses Weekly Repository¹.

Approach

source_conn_github()

To facilitate this diseaystore, a new helper function source_conn_github() which joins the family of source_conn_path().
This function helps retrieve named files from GitHub repository.
If the given source_conn argument points to a folder with a git repo, the repo will be updated and the requested file path will be returned. Instead, if the argument is a (API) link to a GitHub repository, the GitHub API is utilised to retrieve the file path.

In either case, we do some fuzzy matching to retrieve the newest file that is older or simultaneous with the requested date
(encoded in the file name being requested).

Say the only available files are "file_2022-01-01.csv" and "file_2022-06-01.csv" and we request the file "file_2022-05-01.csv", the file path to "file_2022-01-01.csv" is returned.

DiseasystoreEcdcRespitoryViruses

A new diseasystore was added with the following features:

• iliari_rates
• infection_type (ILI or ARI)
• age_group

Known issues

This uses code from a bunch of open PRs.
These need to be merged before this will be rebased and openend.

• Improve table identification #121
• Add default value to diseasyoption #122
• Add a testing suite for diseasystores #123

Checklist

• The PR passes all local unit tests
• I have documented any new features introduced
• If the PR adds a new feature, please add an entry in NEWS.md
• A reviewer is assigned to this PR

Footnotes

1. Note: new tongue-twister: "Respiratory Repository" ↩

[codecov]

Codecov Report

Attention: Patch coverage is 85.71429% with 14 lines in your changes are missing coverage. Please review.

Project coverage is 92.97%. Comparing base (e351ac7) to head (6a3d3e2).

Files	Patch %	Lines
R/source_conn_helpers.R	84.37%	10 Missing ⚠️
R/DiseasystoreEcdcRespiratoryViruses.R	0.00%	3 Missing ⚠️
R/DiseasystoreGoogleCovid19.R	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #124      +/-   ##
==========================================
- Coverage   93.78%   92.97%   -0.81%     
==========================================
  Files          14       16       +2     
  Lines         997     1054      +57     
==========================================
+ Hits          935      980      +45     
- Misses         62       74      +12     

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