Create a simpler approach to data creation for non DBContext input type

[theobat]

We sometimes want something simpler than the current over-generalized approach for data insertion where everything is seen through the lens of a DBContext which essentially is :

{
  tableA: [{recordOfValueA1}, ..., {recordOfValueAn}] -- etc
  tableB: [{recordOfValueB1}, ..., {recordOfValueBn}]
}

An exemple of this is when we want to record a simple junction table with a user id and a entity X id. The DBContext is overly generic in this case.

[theobat]

Document the DBContext assembling function && provide an alternative for simpler cases in :
https://github.com/theobat/massalia/blob/master/src/Massalia/SQLClass.hs#L946