Don't cache connection string, use connection string factory instead

[vgribok]

Current implementation of AddPostgreSql() and PostgreSqlHealthCheck() caches connection string for the lifetime of the running application. This goes against the dynamic nature of IConfiguration that allows dynamic reloading and usage of configuration settings without having to restart the application.

Please follow .NET Core Framework pattern for adding SQL Server health check for an example.

[a-patel]

@vgribok
Could you please share your code for dynamic configuration?

[vgribok]

Here's what I mean:

1. Make health check use connection string factory.
2. Wire in factory in Startup.cs

[a-patel]

Got it. I will add a new feature.
Thanks @vgribok

[a-patel]

I have already started working on upgrading all LiteXHealthChecks to .NET Core 3.0.
I will add factory support for all packages.