Support derived queries using the same field multiple times

Hi,

I am using a sparse index on the field fieldFoo and to best utilize it, I need to add an extra $exists condition before the $eqone.
When I manually create it via a criteria, the object is fine and working:

Document{{fieldFoo=Document{{$exists=true, $eq='123'}}}}

Now trying to achieve it via a repository method:

getByFieldFooExistsAndFieldFoo(String value); // not working - it expects a true/false for the exists part

or

getByFieldFooExistsIsTrueAndFieldFoo(String value); // also not working due to syntax

this workaround syntax appears fine:

getByFieldFooExistsAndFieldFoo(boolean exists, String value); // passing always true

but the current spring-data source code is not supporting it:

org.springframework.data.mongodb.InvalidMongoDbApiUsageException: 
Due to limitations of the org.bson.Document, you can't add a second 'fieldFoo' 
expression specified as 'fieldFoo : 123'; 
Criteria already contains 'fieldFoo : Document{{$exists=true}}'

It appears to be a combination of the MongoQueryCreator and the AbstractQueryCreator, where combinations are not supported.
Instead of simple a and chain of single conditions:

...
criteria.and("fieldFoo").exists(true)
criteria.and("fieldFoo").is("123")
...

we would need a capability of multi-conditions:
...
criteria.and("fieldFoo").exists(true).is("123")
...

Was this not added on purpose, or just not perceived as widely used/needed?

Start by reading MongoQueryCreator and AbstractQueryCreator to trace how the derived method getByFieldFooExistsAndFieldFoo is turned into Criteria. Compare the current single-condition chaining with the requested repeated-field conditions, then add coverage for the repository method and verify that both $exists and $eq are retained without a duplicate-field exception.