Default collation for Mysql

[nicosp]

The current code defaults to utf8mb4_unicode_ci if the collation is not specified for a table.

This could potentially create tables different from the database collation. For example MariaDb 11.8 defaults to "utf8mb4_uca1400_ai_ci".

Migrations should either:

1. Do not offer any default which would cause tables to fallback to the database collation
   or
2. Make the default configurable (including nulls)

I can create a PR for either of these if we have a decision on how to proceed.

[nicosp]

@dereuromark Thank you for the quick response. I think this is a regression because databases created (and had migrations run) with the previous version defaulted to the database collation.

[dereuromark]

We are talking about 5.x here, right?

[nicosp]

@dereuromark 5.x compared to 4.x. I think the previous version got the default collation and passed it to createTable, in effect reverting to the default collation.

[dereuromark]

I adjusted the PR, and I think both makes sense, defaulting and the config setting.
Let me know if that works for you.

[nicosp]

I already tested something similar (removing the default collation entirely) and it worked perfectly. Thanks!