fix mssql and r2dbc integration

[atomfrede]

This PR fixes all issues mentioned in #15032

• using asEntity('User') everywhere
• correcting the mssql r2dbc url
• adding the necessary setting to liquibase migration

closes #15032

---

Please make sure the below checklist is followed for Pull Requests.

• All continuous integration tests are green
• Tests are added where necessary
• The JDL part is updated if necessary
• jhipster-online is updated if necessary
• Documentation is added/updated where necessary
• Coding Rules & Commit Guidelines as per our CONTRIBUTING.md document are followed

When you are still working on the PR, consider converting it to Draft (bellow reviewers) and adding skip-ci label, you can still see CI build result at your branch.

[DanielFran]

@atomfrede @jhipster/developers We are using an explicit liquibase extension sabomichal/liquibase-mssql that allow defining the property identityInsertEnabled="true" to allows explicit values to be inserted into the identity column of a table, so the same as defining "SET IDENTITY_INSERT jhi_user ON/OFF".
The use of this specific extension was due to no support for this MSSQL property in 2009: https://liquibase.jira.com/wiki/spaces/CONTRIB/pages/1998867/MS+SqlServer+Extensions

In the meantime, the support of official MSSQL is up-to-date, so we probably should migrate back to the official liquibase extension.

So there are 2 possibilities:
1 - exclude the use of the property "identityInsertEnabled="true"" explicitly for reactive and define "SET IDENTITY_INSERT jhi_user ON/OFF" only for reactive
2 - Drop use of sabomichal/liquibase-mssql in favour of the liquibase/liquibase-mssql and define "SET IDENTITY_INSERT jhi_user ON/OFF" like in the official extension for both reactive and non-reactive database

[atomfrede]

I would say let's use the official extension.

[atomfrede]

But very strange it doesn't work with identityInsertEnabled property.

[DanielFran]

Liquibase version we are using is version 4 and actually the extension was compatible with version 3, not sure there is any issue with the version 4.

Anyway Liquibase should handle now reactive database also, so I agree the better is to switch with liquibase official extension.

[atomfrede]

@DanielFran Done. Works fine (tested with reactive only though, but don't see why it should not work with classical jdbc).

[DanielFran]

@atomfrede Can you please review tests?

[atomfrede]

@atomfrede Can you please review tests?

On it. Seems easy to fix.

[DanielFran]

@atomfrede LGTM

Maybe we need to delete https://www.jhipster.tech/tips/004_tip_using_ms_sql_server.html

I will take care of the bom

[atomfrede]

Bounty claimed https://opencollective.com/generator-jhipster/expenses/42719.

Regarding the tip, there is already a disclaimer that the tip is not required anymore. But maybe it is time to delete it now.

[pascalgrimaud]

@atomfrede : approved