Avoid type conflicts for properties

[TooLazyToMakeAName]

Does this issue relate to a new feature or an existing bug?

• Bug
• New Feature

What version of Serilog.Sinks.Elasticsearch is affected? Please list the related NuGet package.
All previous.

What is the target framework and operating system? See target frameworks & net standard matrix.

• netCore 3.0
• netCore 2.0
• netCore 1.0
• 4.7
• 4.6.x
• 4.5.x

Please describe the current behavior?
If two properties with the same name but different types are submittet to Elasticsearch the latter property causes its message to be rejected by Elasticsearch.

Please describe the expected behavior?
Some optional feature should be available to avoid type conflicts.