Implement retry for ServerVersion.AutoDetect in AddMySqlDbContext for Pomelo

[bgrainger]

Fixes #1866.

Microsoft Reviewers: Open in CodeFlow

[eerhardt]

Are we sure we want to "double down" on AutoDetect? @lauxjpn indicated it shouldn't be used in production:

#1161 (comment)

[bgrainger]

I know that was the recommendation, but from a GitHub code search it looked like most users (unsurprisingly, really) were taking "the easy way out" and using AutoDetect. (I.e., I saw AutoDetect much more in those code search results than a hardcoded version).

I'm at a little bit of a loss to really know what the "right" approach is:

1. Stop using AutoDetect in Aspire at all: users will have to specify the server version or it will fail at startup.
2. Strongly encourage specification of a ServerVersion in documentation and examples (e.g., sample app uses builder.AddMySqlDbContext<MyDbContext>("Catalog", settings => settings.ServerVersion = "8.3.0");) but keep this current fallback code in case it's omitted.
3. Even more strongly encourage its use by making ServerVersion a parameter to .AddMySqlDbContext().

I guess this all boils down to: keep the fallback or not. If there is no fallback, users must supply ServerVersion and we can debate the ergonomics of how best to accomplish that. Even if we keep the fallback, we could still discuss what affordances should be provided to make it as easy as possible to fall into the pit of success. (Adding a parameter to AddMySqlDbContext probably isn't right, as it makes it much more difficult to use per-environment configuration.)

My gut feeling right now is that even though using AutoDetect is strongly discouraged by Pomelo, it is provided and supported, and most consumers seem to use it. So for reasons of inertia, Aspire should do the same thing and we can discuss how to encourage people not to, or at least provide good examples in the documentation. Thoughts?

[mitchdenny]

@eerhardt I've triaged this into P4 but could you decide whether it needs to go in after snap?

[eerhardt]

LGTM. Thanks for the contribution!

[lauxjpn]

Be aware that if you use ServerVersion.AutoDetect, then generate migrations on your development machine, and your local and production MySQL database servers differ even slightly in their version (just one patch level can be enough), then your generated migrations might not work on your production server.

Also, generating migrations without a locally available database server does fail by default when using ServerVersion.AutoDetect.