[Feature] Mutation support for datawarehouse's

[rohkhann]

Currently the query builders for mutations for data warehouse are not implemented. This feature is to track adding mutation support for graphql endpoint.

[rohkhann]

Some explanation around the design:
Datawarehouse create, update and delete are unable to generate result sets. This is because they do not have support for OUTPUT clause.

Alternate is to:
Create a DbOperationResult entity type and attach it to the mutations of data warehouses.

DpOperationResult entity is added to the graphql schema. This entity has a single field called status that can take up success or failure. (Stored proc has gone with an empty result field – we could do similar )
Schema would look as follows:

With the mutation return type looking as:

The call to the mutation would look as follows:

Code changes in dab:

In the GenerateSqlGraphQLObjects, we add an entity to the root node call DbOperationResult.

During addition of mutation name the return type of the mutation to dbOperationResult:

For multi-db scenario we were using the return type to determine which entity a mutation belongs to. However, since we are using a generic DbOperationResult as the return type, we would need to determine the entity type using another way. This is acheived by adding model directive to the mutation and extracting from there.

Finally, if the mutation succeeds we need to send back the default result json document so code addition for that: