Error when converting GitHub's SPDXv2.3 JSON -> CycloneDX JSON

I get the following error when trying to convert SPDX v2.3 that's produced by GitHub's built-in SBOM generator to CycloneDX JSON.

```
Unhandled exception: System.Text.Json.JsonException: The JSON value could not be converted to CycloneDX.Spdx.Models.v2_2.ExternalRefCategory. Path: $.packages[0].externalRefs[0].referenceCategory | LineNumber: 0 | BytePositionInLine: 2710.
at System.Text.Json.ThrowHelper.ThrowJsonException(String message)
at System.Text.Json.Serialization.Converters.EnumConverter`1.ReadEnumUsingNamingPolicy(String enumString)
at System.Text.Json.Serialization.Converters.EnumConverter`1.Read(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options)
at System.Text.Json.Serialization.Metadata.JsonPropertyInfo`1.ReadJsonAndSetMember(Object obj, ReadStack& state, Utf8JsonReader& reader)
at System.Text.Json.Serialization.Converters.ObjectDefaultConverter`1.OnTryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value)
at System.Text.Json.Serialization.JsonConverter`1.TryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value, Boolean& isPopulatedValue)
at System.Text.Json.Serialization.JsonCollectionConverter`2.OnTryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, TCollection& value)
at System.Text.Json.Serialization.JsonConverter`1.TryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value, Boolean& isPopulatedValue)
at System.Text.Json.Serialization.Metadata.JsonPropertyInfo`1.ReadJsonAndSetMember(Object obj, ReadStack& state, Utf8JsonReader& reader)
at System.Text.Json.Serialization.Converters.ObjectDefaultConverter`1.OnTryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value)
at System.Text.Json.Serialization.JsonConverter`1.TryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value, Boolean& isPopulatedValue)
at System.Text.Json.Serialization.JsonCollectionConverter`2.OnTryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, TCollection& value)
at System.Text.Json.Serialization.JsonConverter`1.TryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value, Boolean& isPopulatedValue)
at System.Text.Json.Serialization.Metadata.JsonPropertyInfo`1.ReadJsonAndSetMember(Object obj, ReadStack& state, Utf8JsonReader& reader)
at System.Text.Json.Serialization.Converters.ObjectDefaultConverter`1.OnTryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value)
at System.Text.Json.Serialization.JsonConverter`1.TryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value, Boolean& isPopulatedValue)
at System.Text.Json.Serialization.JsonConverter`1.ReadCore(Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
at System.Text.Json.Serialization.Metadata.JsonTypeInfo`1.ContinueDeserialize(ReadBufferState& bufferState, JsonReaderState& jsonReaderState, ReadStack& readStack)
at System.Text.Json.Serialization.Metadata.JsonTypeInfo`1.DeserializeAsync(Stream utf8Json, CancellationToken cancellationToken)
at CycloneDX.Spdx.Serialization.JsonSerializer.DeserializeAsync(Stream jsonStream)
at CycloneDX.Cli.CliUtils.InputBomHelper(String filename, ConvertFormat format)
at CycloneDX.Cli.Commands.ConvertCommand.Convert(ConvertCommandOptions options)
at System.CommandLine.Invocation.CommandHandler.GetExitCodeAsync(Object value, InvocationContext context)
at System.CommandLine.Invocation.ModelBindingCommandHandler.InvokeAsync(InvocationContext context)
at System.CommandLine.Invocation.InvocationPipeline.<>c__DisplayClass4_0.<b__0>d.MoveNext()
--- End of stack trace from previous location ---
at System.CommandLine.Builder.CommandLineBuilderExtensions.<>c__DisplayClass23_0.<b__0>d.MoveNext()
--- End of stack trace from previous location ---
at System.CommandLine.Builder.CommandLineBuilderExtensions.<>c__DisplayClass16_0.<b__0>d.MoveNext()
--- End of stack trace from previous location ---
at System.CommandLine.Builder.CommandLineBuilderExtensions.<>c__DisplayClass27_0.<b__1>d.MoveNext()
--- End of stack trace from previous location ---
at System.CommandLine.Builder.CommandLineBuilderExtensions.<>c__DisplayClass25_0.<b__0>d.MoveNext()
--- End of stack trace from previous location ---
at System.CommandLine.Builder.CommandLineBuilderExtensions.<>c.<b__24_0>d.MoveNext()
--- End of stack trace from previous location ---
at System.CommandLine.Builder.CommandLineBuilderExtensions.<>c__DisplayClass22_0.<b__0>d.MoveNext()
--- End of stack trace from previous location ---
at System.CommandLine.Builder.CommandLineBuilderExtensions.<>c__DisplayClass11_0.<b__0>d.MoveNext()
--- End of stack trace from previous location ---
at System.CommandLine.Builder.CommandLineBuilderExtensions.<>c.<b__10_0>d.MoveNext()
--- End of stack trace from previous location ---
at System.CommandLine.Builder.CommandLineBuilderExtensions.<>c__DisplayClass14_0.<b__0>d.MoveNext()
```

In order to replicate the error, go to https://github.com/CycloneDX/cyclonedx-cli/network/dependencies and click on "Export SBOM". Then run the following command to convert that file:
`cyclonedx convert --intput-file ./CycloneDx_cyclonedx-cli_bf58f0.json --input-format spdxjson --output-format json`

Reproduziere den Fehler mit dem gemeldeten von GitHub exportierten SPDX JSON und dem Konvertierungsbefehl. Beginne bei CycloneDX.Spdx.Serialization.JsonSerializer.DeserializeAsync und verfolge dann CycloneDX.Cli.CliUtils.InputBomHelper und CycloneDX.Cli.Commands.ConvertCommand.Convert; abgeschlossen ist die Aufgabe, wenn dieselbe SPDX-Eingabe ohne die gemeldete Ausnahme in CycloneDX JSON konvertiert wird.

Vom Indexierungsmodell aus dem Issue-Text verfasst.