Create migration scripts to change from akka_ schema prefix to pekko_ prefix

[mdedetrich]

This persistence plugin used to store data in databases with the akka_ prefix but it has been changed to pekko_. A migration script should be provided to change this prefix for people coming from akka_

[pjfanning]

@mdedetrich Is this a blocker? Could it just be release noted?

[mdedetrich]

@mdedetrich Is this a blocker? Could it just be release noted?

@pjfanning I wouldn't say this is a release blocker however it would be ideal to have this here especially after #19 is merged on initial release if it doesn't make too much time.

[pjfanning]

The DDL is straightforward. I think most users who migrate from Akka can work it out themselves.

Renaming tables can be a little bit different on different databases. Most databases have good documentation on how to rename tables or how to export data and reimport it.

[nvollmar]

We could advise them in the migration doc that overriding the keys for backwards compatibility is an option to renaming the tables:

    offset-table = "akka_projection_offset_store"
    timestamp-offset-table = "akka_projection_timestamp_offset_store"
    management-table = "akka_projection_management"

[pjfanning]

full qualified configs:

pekko.projection.r2dbc.offset-store {
    offset-table = "akka_projection_offset_store"
    timestamp-offset-table = "akka_projection_timestamp_offset_store"
    management-table = "akka_projection_management"
}