Concurrent eventually consistent service

[wayfarer3130]

In order to ensure that the DICOMweb data is eventually consistent when there is more than one concurrent write, a consistency check needs to be performed until the study is consistent. This service needs to be created and used.
The logic is basically:

1. Do some sort of study update
2. Write the DICOMweb data, using the most recent deduplicated data
3. Schedule a hash check for time + T

Time check is just: Compare the hash values of the currently written deduplicated data against the DICOMweb data. If the hash values don't match, then goto #2 above, otherwise study is consistent.