Repository abstraction API

[kaizimmerm]

Refactoring:

• Provide interface on top of *management implementations.
• Make entities immutable and create proper update methods that state by signature what can be updated.
• Introduce builder pattern for EntityFactory create methods and repository update methods.
• Use IDs in signatures for searches, not complete entities
• Consistent usage of Java 8 Optional in the interfaces (Repo shall never return null!)
• Remove TargetInfo interfaces as this does not belong into the API. The very existence of this object is very Spring Data/JPA specific.
• Consistent usage of paging (make sure that we never query everything)
• Fix DMF model name clashes by means of renaming DMF model in similar pattern to the other APIs.
• Check if we really always ned Page or is Slice sufficient
• Split management services (e.g. DS and DS type)
• Consistent naming of methods (see below)

Remove boiler plate

• Remove external artifact (concept was never finished anyway and does not fit to hawkBit as of today)

Method naming concept (example target management)

// Count all targets
Long count()

// Count by filter parameter (example)
Long countByTargetFilterQuery(@NotEmpty String targetFilterQuery);

//Create entity
List<Target> create(@NotEmpty Collection<TargetCreate> create)
Target create(@NotNull TargetCreate create)

//Delete entities (throws EntityNotFoundException if one element does not exist (at least one not found in collection case))
void delete(@NotEmpty Collection<Long> targetIDs);
void delete(@NotNull Long targetID);
void deleteByControllerId(@NotEmpty String controllerId);
void deleteByControllerId(@NotEmpty Collection<String> controllerId);

//Update Target (throws EntityNotFoundException if one element does not exist (at least one not found in collection case))
List<Target> update(@NotEmpty Collection<TargetUpdate> update);
Target update(@NotNull TargetUpdate update);

//Exist
boolean exists(@NotNull Long targetId)
boolean existsByAssignedDistributionSet(@NotNull Long distributionSetID);

// Read methods
// Find one on technical ID (Optional, no EntityNotFoundException)
Optional<Target> get(@NotNull Long targetId);
List<Target> get(@NotEmpty Collection<Long> targetId);

// Find one on non-ID but unique constraint (Optional, no EntityNotFoundException)
Optional<Target> getByControllerID(@NotEmpty String controllerId);
List<Target> getByControllerID(@NotEmpty Collection<String> controllerId);

// Find one on non-ID but and non unique constraint (Optional, no EntityNotFoundException)
Optional<Target> findFirstByDescription(@NotEmpty String description);

// Query/search repository (page might be empty, no EntityNotFoundException) (note: pageReq always first in signature)
Page<Target> findByAssignedDistributionSet(@NotNull Pageable pageReq, @NotNull Long distributionSetID);