GTFS Diff schema v2-rc1 update

[cka-y]

Summary:

• Changed schema version from 2.0.0 to 2.0.0-rc1 and rename schema file to v2-rc1.json
• Removed all additionalProperties constraints to support extensions
• Added not_compared file status with a reason object (code + message) for files that cannot be meaningfully compared
• Added ignored_columns to file diffs for columns excluded due to unreliable values (e.g. referencing a file that isn't compared)
• Add optional per-file and per-column change statistics (row counts, change percentages, column modification breakdowns)
• Add files_not_compared_count to the summary
• Add validation scripts and a GitHub Action to check JSON syntax and validate examples against the schema

[davidgamez]

Do we need to add total_rows_modified?

[cka-y]

done ✅

[jcpitre]

Whats the diff with rows_modified_count?

[davidgamez]

Sorry, I was too focused on the differences. Here we have a few fields: rows_added_count, rows_deleted_count, and rows_modified_count on a file diff node; then we have the stats on the node with some metrics. We should align these metrics by adding all fields to the root of the diff node and removing the stats node, or moving them all to the stats node(I'm ok either way). And use total_rows_modified or rows_modified_count not both. Thoughts?

[cka-y]

Agreed. I kept all stats in the stats node and have stats exclusively in the file_diff node to avoid duplication

[jcpitre]

2 small comments, but apart from that LGTM!