I'm using mxnet to do some work, but there is nothing when I search the mxnet trial and example.

For example, if there is a relationship transaction.session_id -> sessions.id and we are calculating a feature transactions: sessions.SUM(transactions.value) any rows for which there is no corresponding session should be given the default value of 0 instead of NaN.

Of course this should not normally occur, but when it does it seems more reasonable to use the default_value.

`DirectF

Problem
Since Java 8 was introduced there is no need to use Joda as it has been replaced the native Date-Time API.

Solution
Ideally greping and replacing the text should work (mostly)

Additional context
Need to check if de/serializing will still work.

Is your feature request related to a problem? Please describe.
#878 adds HTTP endpoints and documents such endpoints in Javadoc. However, tools such as OpenAPI does this in a more holistic and visually pleasing manner and is a good to have.

Describe the solution you'd like
Add OpenAPI documentation with Swagger UI.

**Describe altern

It will be nice to have Exploratory Data Analysis (EDA) similar that is in https://mljar.com

The EDA can be saved in a separate Markdown file and have link to it from the main AutoML readme.