Annotate unsupported APIs in Serialization

[StephenMolloy]

Copied from #50526, since this issue references both Serialization and Xml APIs. This copy can be used to track the Xml API.

---

As part of #47228 i am running an analyzer to detect APIs throwing PNSE but not annotated with Obsolete/SupportedOSPlatform/UnsupportedOSPlatform attributes, we need to annotate them so that developers get warnings when they use them unexpectedly

For now, I have results only cross-platform builds, analysis of targeted builds are coming soon where more APIs could be detected

API	Comment	Suggestion	Location
'XmlObjectSerializerReadContextComplex.ResolveDataContractTypeInSharedTypeMode(string, string, out Assembly)'	unconditionally throws on all platforms	add [Obsolete]	libraries\System.Private.DataContractSerialization\src\System\Runtime\Serialization\XmlObjectSerializerReadContextComplex.cs(143,13)
'XsdDataContractExporter.Schemas.get'	unconditionally throws on all platforms	add [Obsolete]	libraries\System.Private.DataContractSerialization\src\System\Runtime\Serialization\XsdDataContractExporter.cs(38,17)
'XsdDataContractExporter.DataContractSet.get'	unconditionally throws on all platforms	add [Obsolete]	libraries\System.Private.DataContractSerialization\src\System\Runtime\Serialization\XsdDataContractExporter.cs(59,17)
'XmlDictionaryReader.CreateMtomReader(Stream, Encoding[], string?, XmlDictionaryReaderQuotas, int, OnXmlDictionaryReaderClose?)'	unconditionally throws on all platforms	add [Obsolete]	libraries\System.Private.DataContractSerialization\src\System\Xml\XmlDictionaryReader.cs(153,13)
'XmlDictionaryReader.CreateMtomReader(byte[], int, int, Encoding[], string?, XmlDictionaryReaderQuotas, int, OnXmlDictionaryReaderClose?)'	unconditionally throws on all platforms	add [Obsolete]	libraries\System.Private.DataContractSerialization\src\System\Xml\XmlDictionaryReader.cs(177,13)
'XmlDictionaryWriter.CreateMtomWriter(Stream, Encoding, int, string, string?, string?, bool, bool)'	unconditionally throws on all platforms	add [Obsolete]	libraries\System.Private.DataContractSerialization\src\System\Xml\XmlDictionaryWriter.cs(68,13)
'XmlCollation.CreateSortKey(string)'	Unsupported on Unux (AnyOS than windows)	make XmlCollation.UpperFirst windows only	libraries\System.Private.Xml\src\System\Xml\Xsl\Runtime\XmlCollation.Unix.cs(24,17)

Note: We are suggesting adding [Obsolete] for the APIs only supported in .Net framework but not supported in .NetCore, with the corresponding Message, DiagnosticId, and UrlFormat

runtime/src/libraries/System.Net.Requests/src/System/Net/AuthenticationManager.cs

Line 17 in cecc76a

[Obsolete(Obsoletions.AuthenticationManagerMessage, DiagnosticId = Obsoletions.AuthenticationManagerDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]

You can claim the next available DiagnosticId from Obsoletions.cs .

cc @jeffhandley @terrajobst @GrabYourPitchforks

[dotnet-policy-service]

Tagging subscribers to this area: @dotnet/area-system-xml
See info in area-owners.md if you want to be subscribed.

[KalleOlaviNiemitalo]

It looks like XmlCollation.UpperFirst is reachable via the XSLT 2.0 xsl:sort/@collation and @default-collation attributes, if the value is a URI that starts with http://collations.microsoft.com and has a query parameter UPPERFIRST=TRUE (case-insensitive). However:

• The XSLT implementation in .NET generally doesn't support XSLT 2.0; there is some code within #if XSLT2, but that symbol is not defined.
• The W3C XSLT 2.0 specification does not mention the Microsoft-specific http://collations.microsoft.com URI. In https://www.w3.org/TR/2017/REC-xpath-functions-31-20170321/#uca-collations, there is instead a different URI http://www.w3.org/2013/collation/UCA with a different query parameter caseFirst=upper.

The xsl:sort/@collation attribute is not documented at https://learn.microsoft.com/en-us/previous-versions/dotnet/netframework-4.0/ms256196(v=vs.100) either. I think Microsoft doesn't have XSLT documentation that would need to be updated to advise users not to attempt UpperFirst collations on non-Windows operating systems.

AFAICT, the xsl:sort/@case-order attribute is not affected. That is translated to XmlCaseOrder.UpperFirst, which is portably implemented in src/libraries/System.Private.Xml/src/System/Xml/XPath/Internal/CompiledXPathExpr.cs.