Merge master (v5.1.0) into openapi branch

[bkoelman]

Aside from the merge itself:

• Updated calls to ArgumentGuard to remove the nameof() parameter
• Fixed Microsoft.SourceLink.GitHub / SauceControl.InheritDoc in OpenAPI project files that produce NuGet packages
• Fixup constraint in tests to require TestableDbContext instead of DbContext

QUALITY CHECKLIST

• Changes implemented in code
• Complies with our contributing guidelines
• Adapted tests
• N/A: Documentation updated

[codecov]

Codecov Report

Merging #1209 (ec52cf7) into openapi (375a0ed) will increase coverage by 0.04%.
The diff coverage is 98.45%.

@@             Coverage Diff             @@
##           openapi    #1209      +/-   ##
===========================================
+ Coverage    92.24%   92.29%   +0.04%     
===========================================
  Files          303      304       +1     
  Lines         8774     8866      +92     
===========================================
+ Hits          8094     8183      +89     
- Misses         680      683       +3     

Impacted Files	Coverage Δ
...Annotations/Resources/Annotations/AttrAttribute.cs	90.00% <ø> (ø)
.../Resources/Annotations/ResourceAttribute.shared.cs	100.00% <ø> (ø)
...urces/Annotations/ResourceLinksAttribute.shared.cs	100.00% <ø> (ø)
...ourceGenerators/TypeWithAttributeSyntaxReceiver.cs	100.00% <ø> (ø)
...ation/JsonConverters/WriteOnlyDocumentConverter.cs	91.66% <ø> (ø)
...Converters/WriteOnlyRelationshipObjectConverter.cs	81.25% <ø> (ø)
...sonApiDotNetCore/Serialization/Objects/Document.cs	100.00% <ø> (ø)
...nApiDotNetCore/Serialization/Objects/ErrorLinks.cs	100.00% <ø> (ø)
...ApiDotNetCore/Serialization/Objects/ErrorObject.cs	95.00% <ø> (ø)
...ApiDotNetCore/Serialization/Objects/ErrorSource.cs	100.00% <ø> (ø)
... and 193 more

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[bkoelman]

@maurei as part of the bits you merged today, the changes from #1218 should be propagated to the OpenAPI projects. Specifically:

• Remove xunit.runner.json files on disk and any references to them in .csproj files.
• In *DbContext classes that override OnModelCreating, call base.OnModelCreating(builder) at the end of the method.

[maurei]

Acknowledged!