Move out mongo syntax from unrelated classes

[e-pettersson-ericsson]

Description

We have hard coded MongoDQ query strings in:

• com.ericsson.ei.subscription.SubscriptionRepeatDbHandler.prepareQueryToUpdateAggregation(String, int, String)
• src/main/java/com/ericsson/ei/handlers/EventToObjectMapHandler.java
• src/main/java/com/ericsson/ei/queryservice/ProcessAggregatedObject.java

These should be extracted in a similar way which MongoQuery was, to abstract away mongo specific syntax from product code.
Tests might need to be added.

Motivation

Keep all Mongo related syntax in "one" place - the Mongo package.

Exemplification

Benefits

Making it easier to change database implementation, if needed, in the future.

Possible Drawbacks