Feat relationships

[abnegate]

What's changed

• Add create/update/delete relationship attributes
• Allow creating documents with relationships, either with existing document ID's or nested documents. If nested documents do not exist, they are created. They are updated if they already exist and the data is different.
• Add fetching documents with relationships. Allows nesting up to a maximum level.
• Add updating documents with relationships.
• Add deleting documents with relationships.
• Allow querying documents with relationships. Will filter parent documents based on child attributes. Uses dot-paths to specify child attributes. E.g. For a one-to-many, author to posts relationship Query::equal('posts.title', ['Post 1']) will return all authors that have at least one post where the title equals 'Post 1'.
• Allow selecting attributes from child relationships. Must either select some or all parent attributes, defaults to all. Uses dot-paths to specify child attributes. Can use wildcard * to specify selection of all a relationships attributes. E.g. Query::select(['posts.title']) or Query::select(['posts.*']) if parent attributes are selected, and relationship attributes are not, relationships are not fetched.

Test Plan

• Added tests covering CRUD for relationship attributes of all types, and CRUD for documents for each type, as well as querying and selecting.
• Performance testing and benchmarking

[christyjacob4]

Looks good. Just some more questions

[christyjacob4]

Looks good 👍