fix(lambda): return correct number of migrated links from lambda functions

[halfwhole]

Problem

Currently, the lambda functions to migrate links between users always returns the number of rows affected as 1, regardless of the actual number of links transferred.

Closes #1806

Solution

• migrate_user_links has been updated to return the actual number of rows affected when updating the urls table
• As for migrate_url_to_user, it might not be necessary to return the number of rows affected, because if not for an error, there should always be exactly 1 link transferred. Is it ok to just remove this then?

Tests

• Test migrate_user_links on staging
• Test migrate_url_to_user on staging

I've tested this locally by running the javascript code on node (without using aws lambda, which I'm not sure how to use yet), and locally it seems to work well

EDIT: have tested invoking the lambda functions both locally and on staging with the help of @yong-jie and it looks good

[yong-jie]

migrate-url-to-user will alwas only have 1 link transferred. Is it ok to just remove this then?

yup sure thing, we can remove it! 👍

Just for future consideration: in general it probably isn't very harmful to be overly-verbose. In an unlikely scenario where something goes wrong with the DB function, and it transfers more than one link at a time, logging the number returned would have helped us detect the problem early.

[yong-jie]

lgtm. tested together with @halfwhole and verified that it works on go-staging. We noted that the DB function does not get deployed automatically with the rest of the CI/CD pipeline, and therefore we will need to manually update the functions prior to release.