Sync attributes between `users` and `user_details`

What does this MR do?

This MR sets up a new table where the rarely used (mostly visible on user's profile) string attributes on users are going to be moved to user_details.

This MR contains:

• Creation of user_details table.
• Set up INSERT and UPDATE trigger on users to sync the values, respecting the newly established validation (LIMIT) rules on user_details.
• Background migration to copy the column data to the user_details table.

Users to migrate: < 400_000 (specialized index is included)

UserDetail limits:

column	default	limit	reasoning
bio	''	255	existing limit on User model
organization	''	255	it was unlimited, couldn't find meaningful organization in the PRD DB (only spam) above 255
location	''	255	it was unlimited, couldn't find meaningful location in the PRD DB (only spam) above 255
linkedin	''	2048	it was unlimited, setting max browser URL length limit
twitter	''	2048	it was unlimited, setting max browser URL length limit
skype	''	2048	it was unlimited, setting max browser URL length limit
website_url	''	2048	it was unlimited, setting max browser URL length limit

Migration rule: Only migrate records when one of the columns are are NOT NULL OR '':

• bio
• location
• organization
• linkedin
• twitter
• skype
• website_url

BG migration query:

INSERT INTO user_details
            (
                        user_id,
                        bio,
                        location,
                        organization,
                        linkedin,
                        twitter,
                        skype,
                        website_url
            )
SELECT id                         AS user_id,
       substring(COALESCE(bio, '') from 1 for 255)          AS bio,
       substring(COALESCE(location, '') from 1 for 255)     AS location,
       substring(COALESCE(organization, '') from 1 for 255) AS orgainzation,
       substring(COALESCE(linkedin, '') from 1 for 255)     AS linkedin,
       substring(COALESCE(twitter, '') from 1 for 255)      AS twitter,
       substring(COALESCE(skype, '') from 1 for 255)        AS skype,
       substring(COALESCE(website_url, '') from 1 for 255)  AS website_url
FROM   "users"
WHERE  ((
                     COALESCE(bio, '') IS distinct FROM '')
       OR     (
                     COALESCE(location, '') IS DISTINCT FROM '')
       OR     (
                     COALESCE(organization, '') IS DISTINCT FROM '')
       OR     (
                     COALESCE(linkedin, '') IS DISTINCT FROM '')
       OR     (
                     COALESCE(twitter, '') IS DISTINCT FROM '')
       OR     (
                     COALESCE(skype, '') IS DISTINCT FROM '')
       OR     (
                     COALESCE(website_url, '') IS DISTINCT FROM ''))
AND    "users"."id" BETWEEN 1 AND    40449
ON conflict (user_id) do UPDATE
set    "bio" = excluded."bio",
       "location" = excluded."location",
       "organization" = excluded."organization",
       "linkedin" = excluded."linkedin",
       "twitter" = excluded."twitter",
       "skype" = excluded."skype",
       "website_url" = excluded."website_url";

Plan

• Plan is for batch size: 1_000
• Around 1s, since the data is not part of the index, we could reduce the batch size to 500.
• Estimated execution time (1_000 batch): ~ 15 hours
• Estimated execution time (500 batch): ~ 30 hours

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Closes #206913 (closed)