Configure collation/charset for DB connection

[Dakad]

Resolves #46

Context

Allow the configuration of the collation to use during the DB.open connection. Just include into the connection string URI &encoding=utf8mb4_unicode_520_ci The charset is deduced from the encoding. Only the collation with their ID below than 1 byte can be used and some collation are not supported by MySQL. See: https://dev.mysql.com/doc/refman/5.7/en/charset-connection.html#charset-connection-impermissible-client-charset

[bcardiff]

If we use a different collation, should the strings sent as arguments be encoded differently? We would need a couple of specs for this change, I fear it could break the support of other collations if there are none.

[straight-shoota]

@Dakad Would it be possible to add some specs for this?

Also note the question in https://github.com/crystal-lang/crystal-mysql/pull/100#issuecomment-1023328125

[Dakad]

@straight-shoota @bcardiff My bad, I completely forgot about this :disappointed: I will add some specs.

About the question, I'm not sure to fully understand it. I expect the ?encoding= param to be in UTF8 since it's a URI::Params

[bcardiff]

I checked with other native driver implementation and it seems they don't do anything to the payload if the collation/charset is different. So extra 👍 on that regard.

[straight-shoota]

All right, then let's merge it 👍

[bcardiff]

Yup. I would drop the unneeded defs I pointed above and merge it. I can take care of it in the following days.

[bcardiff]

Thanks @Dakad for the contribution and my apologies for the long delay in this PR