Ensure Server version generation occurs on sequential manner

[githengi]

We need to ensure that server versions assignment are sequential to ensure API clients to not miss some records.

Below is the implementation plan

• Add a method persist on BaseRepository interface that will be called to save or update a record. It shall accept an entity and boolean new which determines if its an insert or update
• Make the persist method synchronized so that only one thread can execute it a time
• Generate the server version in the persist method so that the server version is generated and record saved in one atomic transaction
• Update the service method to use persist the method
• Remove the calls to generate server version on service methods
• Make the method to generate server version protected/private so that they are only called from the repositories
• Add/Update unit tests
• Add integration tests for OpenSRP task/getAll API seems to miss concurrently-created serverVersions (reveal-stage instance) opensrp-server-web#611 (comment)

[githengi]

The above approach will only work on single server instances. The below changes will be added to support running several OpenSRP servers

• Add server version columns on the main database tables

• Generate the server version during insert or update of record on main table and return on mapper

• Update the server version on entity from the value returned on save/update

• Update the entity with server version and execute update, use primary key for update

• Process the metadata save as is

Update server version generation for

• event
• client
• report
• location
• structure
• location
• plan
• task
• settings
• view configuration