With a defaultValueProvider you're able to have properties like createdAt without the necessity to set the date by hand.
With this we also dropped the UUID as peerDependency.

BREAKING CHANGE:
`@PartitionKeyUUID()` does no longer exist. Use `@Property({ defaultValueProvider: uuidGeneratorFunction })` instead

# Conflicts:
#	src/decorator/metadata/metadata.ts
#	src/mapper/mapper.ts

[skip release]

BREAKING CHANGE: empty strings are now valid dynamoDB values (see https://aws.amazon.com/about-aws/whats-new/2020/05/amazon-dynamodb-now-supports-empty-values-for-non-key-string-and-binary-attributes-in-dynamodb-tables/ for official statement) and thus they are mapped to and from db.

feat(empty-strings): drop empty string strictness to allow new empty string feature

#91 default value provider

make sure next is released on next channel with prerelease tag