Adding pagination support

[mbhaskar]

This PR adds pagination support to the queries.

Schema design

We use connection objects to achieve pagination along with first and after keywords
For example, A list query today looks like below

type Query{
  planets : [Planet]
}

To paginate instead of fetching all the results like the above query, we use a page size and a connection object which would return the nodes as result list and a continuation which would help us obtain next page.
We use first as a keyword for page size and after as a keyword for specifying continuation. Here is how the schema should look like

type Query{
 planets(first: Int, after: String): PlanetConnection
}

type PlanetConnection{
 nodes: [Planet]
 endCursor: String
 hasNextPage: Boolean
}

A null continuation in the result would mean there are no more results.
A base64 encoded continuation token looks like this: W3sidG9rZW4iOiItUklEOn5saHQxQVBKZFpPMERBQUFBQUFBQUFBPT0jUlQ6MiNUUkM6MyNJU1Y6MiNJRU86NjU1NjcjUUNGOjQiLCJyYW5nZSI6eyJtaW4iOiIiLCJtYXgiOiJGRiJ9fV0=

Resolver design:
Resolver should now have a "isPaginated" property set to true to identify a query as a paginated query
ex:
{
"id": "planets",
"isPaginated": true,
"databaseName": "graphqldb",
"containerName": "planet",
"parametrizedQuery": "select * FROM c"
}

This PR

• Fixes Cosmos DB: Paginated Query #7
• Adds support for above schema to paginate over the results
• Adds support for list types in sub objects

** This PR contains some double deserialization serialization which happens because of the conversions between Netwonsoft and System.Text.Json. Since System.Text.Json seems to have limited capabilities in json writing/creating, I will be removing this and move the code to use only Newtonsoft which will also avoid the problem of mutliple serializations. Created an issue for the same #60

corresponding RFC: https://github.com/Azure/project-hawaii/blob/main/rfcs/cursor-connection-pagination.md

References:
Pagination in cosmosdb: https://docs.microsoft.com/en-us/azure/cosmos-db/sql/sql-query-pagination

[jarupatj]

Can we please add tests.

[jarupatj]

🕐

[jarupatj]

We need a spec on the other repository.

[jarupatj]

what is the plan for adding support for SQL and PG?

[mbhaskar]

what is the plan for adding support for SQL and PG?

In this PR, we are modifying the query interface to indicate if this is a continuation query, and also pass the first and after values. Adding detailed implementation is something we have to work with respective service implementation @Aniruddh25 lets syncup?

[JelteF]

@mbhaskar Can you update this according to the modified RFC.

Merged RFC PR: https://github.com/Azure/project-hawaii/pull/20
RFC: https://github.com/Azure/project-hawaii/blob/main/rfcs/cursor-connection-pagination.md

[JelteF]

Also, I think it's good to have this PR only implement the Cosmos side and do PG and SQL afterwards. That way there's a base for PG and SQL to build on.

[JelteF]

Apart from the comments I left, there's some merge conflicts again now that my SQL query generation PR got merged.

Part of my comments is advice on how to make the tests more readable and maintainable. Feel free to ignore this for now, it can be addressed in a future PR dedicated to it as well if you prefer.

[seantleonard]

Thanks for queueing up these changes! Would like to see additional elaboration in some sections RE: comments I've left. Also, in your PR description could you include a sample query or two that can be copy pasted into a request body to quickly test your functionality?

[JelteF]

thanks for addressing the comments

[jarupatj]