Make Permissions property optional on ProjectTask

[brentonrace]

Make Permissions property optional on ProjectTask to match data returned from Toggl API

[brentonrace]

As of last night, we are getting following error when retrieving Tasks. I can see the JSON returned from the API simply does not include the permissions property on any records. If I understand the issue correctly, this change should fix the property to be optional when deserializing.

Refit.ApiException: An error occured deserializing the response.
 ---> System.Text.Json.JsonException: JSON deserialization for type 'Toggl.Api.Models.ProjectTask' was missing required properties, including the following: permissions
   at System.Text.Json.ThrowHelper.ThrowJsonException_JsonRequiredPropertyMissing(JsonTypeInfo parent, BitArray requiredPropertiesSet)
   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.DeserializeAsync(Stream utf8Json, CancellationToken cancellationToken)
   at System.Net.Http.Json.HttpContentJsonExtensions.ReadFromJsonAsyncCore[T](HttpContent content, JsonSerializerOptions options, CancellationToken cancellationToken)
   at Refit.SystemTextJsonContentSerializer.FromHttpContentAsync[T](HttpContent content, CancellationToken cancellationToken)
   at Refit.RequestBuilderImplementation.DeserializeContentAsync[T](HttpResponseMessage resp, HttpContent content, CancellationToken cancellationToken)
   at Refit.RequestBuilderImplementation.<>c__DisplayClass14_0`2.<<BuildCancellableTaskFuncForMethod>b__0>d.MoveNext()