Implement versioned item functionallity

[dkraczkowski]

Description

amano.VersionedItem class should automatically recognised by save, put and update commands as a versioned (event sourced) entity. Each time a write is made with a versioned item, there should be two writes:

• write to version 0
• write to version n, where n is an integer number increased every time item is persisted.

Version of the item should be kept as a part of sort-key. The following is the schema for the versioned sort-key:

{n}:{sort_key}

• n is the version number
• sort_key is the user's sort key

Every time read operation is made to a versioned item with a condition, that condition should be automatically ammended and sort key should be either added or modified in the expression to filter only for the latest version 0.

This behaviour can be easily ignored in the userland if two representations are made for the same item, one is versioned the other is a normal item.

References

• amano.VersionedItem

Test case scenarios

TBC