Implemented a customized WithMockUser and
WithMockUserSecurityContextFactory to mock an Authentication with User
and UserProfile.

* AuthenticationProvider-agnostic User object allows access to common
  user attributes: userId, loginId, authProvider, etc.
* Auto-create UserProfiles for external accounts
* Use userId (instead of loginId) for permission checks
* Use custom implementation for Pac4j integration
  (remove org.pac4j.spring-security-pac4j)
* Move authentication logic from controller to service layer
* Remove user room role handling
* Rename targetDomainType 'session' to 'room'

Moved PI timer logic to its own service. The implementation for room
owner changes has been removed for now.

A new service, repository and entity have been introduced to handle file
attachments to other entities. Attachments store meta data about the
file. The file upload is not yet implemented. It is planned to abstract
the storage handling to allow the support for different storage
solutions (local file system, database, cloud).

Marius Renner authored 7 years ago and Daniel Gerhardt committed 6 years ago

Cast int to double before division to avoid truncation of the division
result. Changed corresponding test so that it fails with the old
implementation.

Cherry-picked and backported from GH-52.

Implemented a patch method which merges an existing entity with updated
properties from a HashMap. A new test dependency spring-security-test
has been added.

* Moved classes from `de.thm.arsnova` root package.
* New util package
* Do not start interface names with `I`. Appended `Impl` to the
  implementing class instead.
* Renamed learning progress classes to score and move them from
  `.domain` to a new `.services.score` package.
* Do not capitalize acronyms in class names:
    * CASLogoutSuccessHandler -> CasLogoutSuccessHandler
    * SocketIO* -> Socketio*
* Renamed `.socket` package to `.websocket`

Mosts of the tests were coupled with the old database layer.
Additionally, a lot of them were testing simple CRUD operations intead
of domain logic. Meaningful tests with proper database mocking have to
be written at a later time.

Code for the following domains has been migrated:
* VisitedSession
* MotdList
* Statistics
* LearingProgress

(Lecturer/Skill)Question has been renamed to Content. Method names have
not been touched yet to ease reviewing the changes.

InterposedQuestion has been renamed to Comment. Method names have not
been touched yet to ease reviewing the changes.

LoggedIn documents are also handled by the SessionRepository for now.

This improves/fixes compatibility with third-party OAuth APIs.

All former features of NovaView have been merged into CouchDB4J so it
is no longer needed.

The following replacements have been made:
* New design document name
    - New view name: (conditions) keys => values
        * Full old view name: (conditions) keys => values

* content/
    - by_sessionid: sessionId => _rev
        * skill_question/count_by_session: sessionId => doc
    - by_sessionid_variant_active: sessionId, questionVariant, active, subject, text.substr() => _rev
        * skill_question/by_session_only_id_for_all: (active == 1) sessionId => null
        * skill_question/flashcard_count_by_session: (questionVariant == "flashcard") sessionId => doc
        * skill_question/lecture_question_count_by_session: (questionVariant == 'lecture') sessionId => doc
        * skill_question/lecture_question_ids_by_session_and_subject: (questionVariant == 'lecture') sessionId, subject => _id
        * skill_question/lecture_question_ids_by_session_for_all: (questionVariant == "flashcard" && active == 1) doc.sessionId, doc.subject, doc.text => {}
        * skill_question/lecture_question_subjects_by_session: (questionVariant == 'lecture') sessionId => subject
        * skill_question/preparation_question_count_by_session: (questionVariant == 'preparation') sessionId => doc
        * skill_question/preparation_question_ids_by_session_and_subject: (questionVariant == 'preparation') sessionId, subject => _id
        * skill_question/preparation_question_ids_by_session_for_all: (questionVariant == 'preparation' && active == 1) sessionId, subject, text => {}
        * skill_question/preparation_question_subjects_by_session (questionVariant == "preparation") sessionId => subject
    - doc_by_sessionid_variant_active: sessionId, questionVariant, active, subject, text.substr() => doc
        * skill_question/by_session: sessionId, subject => doc
        * skill_question/by_session_for_all_full: (active == 1) sessionId, subject, text => doc
        * skill_question/by_session_sorted_by_subject_and_text: sessionID, subject, text => doc
        * skill_question/flashcard_by_session: (questionVariant == 'flashcard') sessionId, subject, text => doc
        * skill_question/flashcard_by_session_for_all: (questionVariant == "flashcard" && active == 1) sessionId, subject, text => doc
        * skill_question/lecture_question_by_session: (questionVariant == 'lecture') sessionId, subject, text => doc
        * skill_question/lecture_question_by_session_for_all: (questionVariant == 'lecture' && active == 1) sessionId, subject, text => doc
        * skill_question/preparation_question_by_session: (questionVariant == 'preparation') sessionId, subject, text => doc
        * skill_question/preparation_question_by_session_for_all: (questionVariant == 'preparation' && doc.active == 1) sessionId, subject, text => doc

The following views have been removed:
* skill_question/questions_by_ids: _id => doc (use all_docs)

SessionServiceTest.testShouldDeleteAllSessionData fails when run on
JDK 8.

* Remove unused code
* Optimize imports (group 10+ and static imports)
* Remove redundant variable assignments
* Replace explicit type parameters with <>
* Remove redundant catch blocks
* Use varargs instead of explicit array instantiation
* Weaken visibility of methods and fields
* Simplify conditions
* Do not use StringBuilder for simple concatenations
* Fix code style
* Remove invalid Javadoc