feat(quotations): describe how a union is written

.github/copilot-instructions.md

@@ -12,6 +12,13 @@
 
 ```text
 /
+├── src/Cosmos.Quotations/ – translator of F# quotations into queries (FSharp.Azure.Cosmos.Quotations), built stage by stage and not packed yet
+│   ├── TranslationError.fs – translation errors and the place of a quotation in the source
+│   ├── Normalizer.fs    – normal form of a quotation
+│   ├── Evaluator.fs     – value of a part of a quotation that reads no variable
+│   ├── Query.fs         – functions that say whether a value is a constant or a parameter of the query
+│   ├── Parameterizer.fs – shape of a quotation, by which its translation is found again, and the values of its parameters
+│   └── JsonLayout.fs    – how the serializer writes the members of a document: their names and what a member without a value is
 ├── src/Cosmos/          – main library (FSharp.Azure.Cosmos)
 │   ├── SubStatusCodes.fs – documented Cosmos DB sub-status codes
 │   ├── Cosmos.fs        – core types and container extensions
@@ -28,6 +35,7 @@
 ├── src/Shared/          – source files that every F# project under src and tests compiles
 │   └── ValueCollections.fs – `Seq`, `List` and `Array` functions that return `voption` and struct tuples
 ├── tests/Cosmos.Tests/  – MSTest integration test project
+├── tests/Cosmos.Quotations.Tests/ – MSTest unit tests of FSharp.Azure.Cosmos.Quotations, no emulator needed
 ├── tests/Cosmos.Tests.Infrastructure/ – shared test fixtures, emulator settings and assertion helpers
 ├── build/               – FAKE build scripts
 └── docsSrc/             – FSharp.Formatting documentation source
@@ -39,6 +47,7 @@
 * [`FSharp.Control.TaskSeq`](https://github.com/fsprojects/FSharp.Control.TaskSeq) – `IAsyncEnumerable` / `taskSeq` support
 * [`FSharp.Control.Reactive`](https://github.com/fsprojects/FSharp.Reactive) – Rx extensions for F#
 * [`FsToolkit.ErrorHandling`](https://github.com/demystifyfp/FsToolkit.ErrorHandling) – `taskResult`, `Result`, `voption` CEs
+* [`FSharp.SystemTextJson`](https://github.com/Tarmil/FSharp.SystemTextJson) – F# types in `System.Text.Json`; `FSharp.Azure.Cosmos.Quotations` reads its options to know how documents are written
 * [`Unquote`](https://github.com/SwensenSoftware/unquote) – test assertions
 * [`MSTest`](https://github.com/microsoft/testfx) – test framework
 

Directory.Packages.props

@@ -8,6 +8,7 @@
     <PackageVersion Include="FSharp.Control.Reactive" Version="6.1.2" />
     <PackageVersion Include="FSharp.Control.TaskSeq" Version="1.0.0" />
     <PackageVersion Include="FSharp.Core" Version="10.0.100" />
+    <PackageVersion Include="FSharp.SystemTextJson" Version="1.4.36" />
     <PackageVersion Include="FsToolkit.ErrorHandling" Version="5.0.0" />
     <PackageVersion Include="IcedTasks" Version="0.11.10-beta001" />
   </ItemGroup>

FSharp.Azure.Cosmos.slnf

@@ -2,7 +2,9 @@
   "solution": {
     "path": "FSharp.Azure.Cosmos.slnx",
     "projects": [
+      "src\\Cosmos.Quotations\\FSharp.Azure.Cosmos.Quotations.fsproj",
       "src\\Cosmos\\FSharp.Azure.Cosmos.fsproj",
+      "tests\\Cosmos.Quotations.Tests\\FSharp.Azure.Cosmos.Quotations.Tests.fsproj",
       "tests\\Cosmos.Tests.Infrastructure\\FSharp.Azure.Cosmos.Tests.Infrastructure.fsproj",
       "tests\\Cosmos.Tests\\FSharp.Azure.Cosmos.Tests.fsproj"
     ]

FSharp.Azure.Cosmos.slnx

@@ -10,7 +10,9 @@
     <File Path="README.md" />
   </Folder>
   <Project Path="build/build.fsproj" />
+  <Project Path="src/Cosmos.Quotations/FSharp.Azure.Cosmos.Quotations.fsproj" />
   <Project Path="src/Cosmos/FSharp.Azure.Cosmos.fsproj" />
+  <Project Path="tests/Cosmos.Quotations.Tests/FSharp.Azure.Cosmos.Quotations.Tests.fsproj" />
   <Project Path="tests/Cosmos.Tests.Infrastructure/FSharp.Azure.Cosmos.Tests.Infrastructure.fsproj" />
   <Project Path="tests/Cosmos.Tests/FSharp.Azure.Cosmos.Tests.fsproj" />
 </Solution>

src/Cosmos.Quotations/AssemblyInfo.fs

@@ -0,0 +1,23 @@
+// Auto-Generated by FAKE; do not edit
+namespace System
+open System.Reflection
+
+[<assembly: AssemblyTitleAttribute("FSharp.Azure.Cosmos.Quotations")>]
+[<assembly: AssemblyProductAttribute("FSharp.Azure.Cosmos")>]
+[<assembly: AssemblyVersionAttribute("1.2.0")>]
+[<assembly: AssemblyMetadataAttribute("ReleaseDate","2026-10-01T00:00:00.0000000+02:00")>]
+[<assembly: AssemblyFileVersionAttribute("1.2.0")>]
+[<assembly: AssemblyInformationalVersionAttribute("1.2.0")>]
+[<assembly: AssemblyMetadataAttribute("ReleaseChannel","release")>]
+[<assembly: AssemblyMetadataAttribute("GitHash","210cf041a0ce44fcc5a5df369550a77a1f75d436")>]
+do ()
+
+module internal AssemblyVersionInformation =
+    let [<Literal>] AssemblyTitle = "FSharp.Azure.Cosmos.Quotations"
+    let [<Literal>] AssemblyProduct = "FSharp.Azure.Cosmos"
+    let [<Literal>] AssemblyVersion = "1.2.0"
+    let [<Literal>] AssemblyMetadata_ReleaseDate = "2026-10-01T00:00:00.0000000+02:00"
+    let [<Literal>] AssemblyFileVersion = "1.2.0"
+    let [<Literal>] AssemblyInformationalVersion = "1.2.0"
+    let [<Literal>] AssemblyMetadata_ReleaseChannel = "release"
+    let [<Literal>] AssemblyMetadata_GitHash = "210cf041a0ce44fcc5a5df369550a77a1f75d436"