Aspnetcore3

[TiagoBrenck]

Purpose

Updated all the samples to core 3.0
Updated all the texts that were mentioning the dotnet core version

Does this introduce a breaking change?

The dotnet core 3.0 changes made, are not compatible with the previous version.

[x] Yes
[ ] No

Pull Request Type

What kind of change does this Pull Request introduce?

[ ] Bugfix
[x] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Documentation content changes
[ ] Other... Please describe:

How to Test

Please download dotnet core 3.0.

Other Information

Steps done in all samples:

1. Changed target framework to 3.0
2. Edited csproj and remove the package Microsoft.AspNetCore.App because it doesnt exist on 3.0
3. Updated other nuget packages to version 3.x
4. Changed appsettings LogLevel (to match VisualStudio generated template)
5. Adapted Program.cs and Startup.cs to version 3.0 (here is where the changes are not compatible)
6. Removed IIS Express from launchSettings (this is an unknown behavior since a VS generated template uses IIS Express. However, converting our samples and using IIS Express was resulting into an IIS error.
7. Updated README texts that were referencing the dotnet core version