Add FsCodec.SystemTextJson re #14

[bartelink]

Extracted from work by @ylibrach in jet/equinox#197 jet/equinox#200 re #14

Intended as a drop-in replacement for FsCodec.NewtonsoftJson that can be used by 'simply' 'just' replacing the top level namespace and the assembly reference in your source code

• Introduces FsCodec.SystemTextJson, together with a .Tests assembly
• Electing to rename Settings to Options to match STJ naming conventions
• Adds JsonOptionConverter as a shim (as of STJ 4.7, F# options are still not supported out of the box 😿User Story: Developers using JsonSerializer want it to handle common F# types well dotnet/runtime#29812)
• Adds JsonRecordConverter as a shim (as of STJ 4.7, F# records are still not supported out of the box 😿User Story: Developers using JsonSerializer want it to handle common F# types well dotnet/runtime#29812) JsonRecordConverter removed prior to merge, see Require STJ v5; Remove JsonRecordConverter #49 👇
• Port Codec
• Port JsonIsomorphism Port JsonIsomorphism from Newtonsoft variant #40
• Port TypeSafeEnumConverter Port TypeSafeEnum and Converter to System.Text.Json #41
• Prevent over-escaping of HTML-like things re Default to preventing over-escaping in FsCodec.SystemTextJson standard profile #44 Default to not over-escaping in SystemTextJson re #44 #45
• Make OptionConverter symmetric by making Some null render as per None Document handling of Some null as not being special-cased Remove Some null handling wart #39
• Extract FsCodec.Box.Codec to FsCodec.Box package Extract FsCodec.Box.Codec to its own package #46
• STJ: Add ToByteArrayCodec/ToJsonElementCodec shims #48 Provide .ToByteArrayCodec() and ToJsonElementCodec() overloads on SystemTextJson and NewtonsoftJson converters respectively to enable Stores to be able to pick one or the other
• Require STJ v5; Remove JsonRecordConverter #49 Require STJ 5.0.0-preview.3 dependency so we don't need a JsonRecordConverter anymore
• Readme
• [ ] Port UnionConverter Port UnionConverter to STJ #43 deferred, noted in README.md - Port UnionConverter to STJ #43 is pretty complete but needs rebasing and final tweaks; The intent is @NickDarvey will complete this work - there's no eta at present due to competing demands on his time

[fluxlife]

Any chance there could be a beta release of this?

[bartelink]

@fluxlife Good question - this is pretty much ready to go, so we have choices

1. literally release a beta from this branch like you said
2. ping @NickDarvey re whether/when Port UnionConverter to STJ #43 will be fully ready (it's OK if that's a few days, more trying to get a rough idea), then we merge this and release 2.1.0
3. merge this, release 2.1.0, let Port UnionConverter to STJ #43 release as a fast-follow 2.1.0
4. @ylibrach when 2 or 3 happens, I'll apply it to feat!(CosmosStore): Azure.Cosmos 'V4' support / enable mocking Cosmos APIs equinox#197 and do another alpha out there too - would also appreciate a quick scan by you for any stuff we should fix in this PR/branch before baking this as the final 2.x era API for FsCodec.SystemTextJson

[bartelink]

Hopefully FsCodec.SystemTextJson (i.e. this PR) can have the JsonRecordConverter removed soon; it seems that dotnet/runtime#29812 has been prioritized in https://github.com/dotnet/runtime/projects/25#card-35157538

eta: Done in #49

[bartelink]

@fluxlife merging/releasing now