npm-health: Implement collection and metrics in GrimoireLab, including the score calculation

[pombredanne]

[canasdiaz]

The code will be published at https://github.com/aboutcode-org/healthycode

[dicortazar]

Initial set of metrics is a compendium of the following:

• coefficient_of_variation
• commit_size_added_lines
• commit_size_removed_lines
• commits_over_periods_rate
• commits_per_month
• commits_per_week
• commits_per_year
• contributor_growth_rate
• days_since_last_commit
• developer_categories_casual
• developer_categories_regular
• file_types_other
• message_size_mean
• message_size_median
• message_size_total
• recent_commits
• recent_contributors
• recent_organizations
• returning_contributors
• total_contributors
• total_organizations

And the following:

• active_branches
• casual_regular_contributors_rate
• contributor_growth
• developer_categories_core
• elephant_factor
• file_types_binary
• file_types_code
• found_file_adopters
• found_file_license
• pony_factor
• total_commits

All those in the first group will be ignored as there's a high correlation between those and some of the second group. Correlation has been defined as any value higher than 0.8.

In addition, from the second group, as they may not be related to the health of projects, file_types_binary, file_types_code, found_file_adopters, found_file_license will be removed.

This leaves the analysis for the following metrics as they're independent between them.

• active_branches
• casual_regular_contributors_rate
• contributor_growth
• developer_categories_core
• elephant_factor
• pony_factor
• total_commits

As further discussion and left for another iteration, we should consider:

• Adding metrics that bring together two or more of the previous ones. An example would be the workload adequacy discussion.
• Adding metrics from other data sources.
• Discuss if the existence of certain files as the adopters file is a symptom of a healthy project.

[dicortazar]

We have already the scores, we need to translate this into Python. This was done at #2164 .