Removed the requirement for having the default constructor in the aggregation process and projections

[oskardudycz]

Overview

Currently, Marten forces in many places new () constructor. This is not a huge issue, but a bit painful and sometimes too big restriction. For most of the guides of how to construct proper aggregates (and classes in general), it stated that they should only expose what's needed. Usually, it's good to not expose the public default constructor but use the dedicated factory method.

Especially for the event-sourced aggregates, it's important, as the state should be rebuilt from the events.

Details of changed

Introduced new object factory called (surprise!) New. This solution is taken from https://stackoverflow.com/a/16162475/10966454.

See also more benchmarks and discussion about object creation from lambda (with expression caching):

• http://grantbyrne.com/post/activatorcreateinstancealternativetesting/
• https://codereview.stackexchange.com/questions/151167/accessing-properties-by-name

The solution tries to find the default public constructor, if it's not able then it's searching for non-public and this is also not found then it creates an uninitialized object (see https://docs.microsoft.com/en-us/dotnet/api/system.runtime.serialization.formatterservices.getuninitializedobject?view=netframework-4.8).

Besides that:

• added necessary tests,
• updated aggregate & repository case study,
• updated documentation with information about object creation,
• copied .editorconfig file to be located in the same folder as marten solution file (this is required to have rules properly applied).

[jeremydmiller]

@oskardudycz I think this all looks good to me.