Add support for alternative MySqlConnector

[ngbrown]

It was suggested by @303248153 to include MySqlConnector in addition to MySql.Data. It may provide better .Net Core support (#633) and has a different license.

This would be enabled by #626.

[fredericDelaporte]

We have to settle whether we wish to have alternate drivers handled by NHibernate team or let the community publish it as an independent packages once #626 is live.

Handled by us:

• more things to maintain.
• maybe less delays in publishing up-to-date versions when a breaking change mandates it.

Handled by anyone else who wishes:

• less work on NHibernate team, letting more time to focus on core features
• may left some data providers in a stale state, unusable with latest NHibernate for long, a bit like what we can witness with caches providers for NHibernate v5. (Redis and EnyimMemcache (on NuGet) still not updated the last time I have looked (and I have sent a message to Enyim NuGet owner), although at least for Redis there are people awaiting it, but apparently not involved enough to do the change themselves. Note that for abandoned package on NuGet, the delay to claim ownership is at least one month, the other solution being to publish a dup, which is not fine.)

[hazzik]

I would prefer the approach with a separate repository under the https://github.com/nhibernate/ organization. This will solve the above concerns. The core team will have less work but will be able to release a new version if there are breaking changes. Also, this does not even require the #626 to start. Just create a new repo and that's it.

[hazzik]

Created a new repo: https://github.com/nhibernate/NHibernate.MySqlConnector

[EmaX093]

Another plus is that the MySqlConnector alternative support real async operations unlike the official connector

[jemiller0]

Any word on if this will be supported sometime soon? I see the repo, but, it looks like it's just empty.

[fredericDelaporte]

It needs someone willing to contribute it. It can be you.

[razzmatazz]

Hi, I have added a PR for this in nhibernate/NHibernate.MySqlConnector#1 with the code that I am using in production. However, there are a couple of things I am not sure what to do about – from PR:

• how to build a nuget package
• should we provide support for multiple frameworks in .csproj (as it uses .netstandard2.0 now)
• what version of NHibernate should I reference in .csproj (now it has 5.2.1 specified)