ENH: Refactor issues to pages script

[jhlegarreta]

Refactor issues to pages script with a focus on the possibility to be able to re-use methods, and make eventual changes be more localized.

[jhlegarreta]

Partially addresses #25: making the appropriate changes to extract data from the current issue forms is left for a separate PR.

Tested with the BHG 2020 issues. The result is exactly the same as with the previous implementation.

A few notes:

• The list of issues is walked a few times more, but IMHO performance is not an issue here, and I'd say that it is preferable to be able to re-use methods. Improvements can be made in separate PRs.
• Cross-referencing https://github.com/brainhackorg/global2021/pull/32#pullrequestreview-766086517: eventually, part of the code should be the the same to gather issue data for brainmatch (essentially, getting the list of issues, and getting the list of GitHub labels for each issue).
• The script could be split into at least two modules, one containing the methods that can be re-used, leaving in the issues_to_pages.py script only the body of the main so that the issue-to-page.yml workflow can work. This would also allow the methods to get tested (e.g. by downloading the issues available at a given data, and saving them to have some testing data) so that we ensure that this is stable across time, avoid breaking things, and hopefully avoiding to do re-do things year after year.

[Remi-Gau]

* The list of issues is walked a few times more, but IMHO performance is not an issue here, and I'd say that it is preferable to be able to re-use methods. Improvements can be made in separate PRs.

Agreed.

* Cross-referencing [[INFRA] add github issue form #32 (review)](https://github.com/brainhackorg/global2021/pull/32#pullrequestreview-766086517): eventually, part of the code should be the the same to gather issue data for `brainmatch` (essentially, getting the list of issues, and getting the list of `GitHub` labels for each issue).

Agreed. Opened an issue from your other comment. Will make the changes on the form.

* The script could be split into at least two modules, one containing the methods that can be re-used, leaving in the `issues_to_pages.py` script only the body of the main so that the `issue-to-page.yml` workflow can work. This would also allow the methods to get tested (e.g. by downloading the issues available at a given data, and saving them to have some testing data) so that we ensure that this is stable across time, avoid breaking things, and hopefully avoiding to do re-do things year after year.

Will open an issue with this comment to keep track of this.