Implement some unit test cases for the observer.processSegment method and fix a bug found by these tests.
A production snapshot is more certain but it's huge for having in the repository and run the test with it by the CI.
We want to have tests for the different cases to detect zombie segments and relaying on production data cannot guarantee to have all of them.
NOTE the test has been implemented with random values for not having always the same combination of segments list and the same values avoiding that the implementation gets stale due to the test. The issue about this is that it's harder to understand and we could get only sometimes failures in the CI in case that the implementation has some bug.
The random tests allow to eventually check cases that a static test may now cover because it is not expressed or because it is needed to implement a large number of cases.
Because we are worried that the test implementation is complex and we could have bugs on it despite that the same bugs should exist in both, the implementation and the test, moreover that we have to consider that the implementation and the tests have been written by different people. Because of that, we may replace entirely these random tests by a list of static ones.
* Move the observer implementation and the type definitions related with
it and helper functions to its own file.
* Cluster struct type is used as a key for a ObjectsMap type.
Observer struct type has a field of ObjectsMap.
Cluster has a field for project ID.
Observer processSegment method uses its ObjectMap field for tracking
objects.
However Observer processSegment clears the map once the projectID
diverges from the one kept in the Observer lastProjectID field, meaning
that it isn't needed to keep the projectID as part of the ObjectMap key.
For this reason, ObjectMap can use as a key just only the bucket name
and Cluster struct isn't needed.
Because of such change, the ObjectMap type has been renamed to a more
descriptive name.
* Make the types defined for this specific package not being exported.
* Create a constructor function for observer to encapsulate the map
allocation.
* Don't throw away the entirely buckets objects map when an empty one
is used to reuse part of the allocations.
Encapsulate the clearing up logic into a method.
* Make the analyzeProject function to be a method of observer.
