Support string tenant_id; change tenancy

[ramontayag]

• Requires More standard engine config #65

This is a breaking change. See notes in CHANGELOG.md.

[pjohnmeyer]

Hello, long time plutus watcher first time commenter. 😃

@ramontayag I was wondering, why did you decide to, essentially, make multi-tenancy "always-on" and polymorphic as part of this pull? I can see that it simplifies some things a good bit, but it also seems like a separate change from the "support string tenant_id" change.

Also, doesn't plutus already support stringy tenant id's? Perhaps it's not obvious from the documentation, but I believe this "just works" today, if you change the column type before running the multi-tenancy migration.

[ramontayag]

@pjohnmeyer - you're right! It is separate and should be a separate pull request. I'll change it.

As for your second question: yes it will work if you change it before running the migrations.

[ramontayag]

@pjohnmeyer, thanks for pointing that out. Cheers!

#79