Uniform handling for H2 databases

[iluwatar]

At the moment, many of the patterns utilize H2 databases to demonstrate data access (search for jdbc:h2). The problem is that we don't have a unified approach. Some of the patterns use file-based database written somewhere under the home directory and some use in-memory databases. Perhaps we could use in-memory databases everywhere so the user's disk would not be cluttered? If not possible, at least store the database files under the same directory.

Acceptance criteria

• H2 database handling is unified

[shivu2002a]

@iluwatar Can I work on this issue?

[Pratik-kp]

I would like to work on this issue, can I join?

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. The issue will be unassigned if no further activity occurs. Thank you for your contributions.

[takikuba]

Hello, I don't see any PR related to this problem. I still see both h2 db versions in the code, please assign this to me.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. The issue will be unassigned if no further activity occurs. Thank you for your contributions.