* Setup leader state machine functions

* Datastructure and test setup

* Skeletonizign

* First test code passes

* Implement Leadership election

* Implement some tests for running a leaderelection campaign

* velocyPackHell

* add forgotten file

* Split work up

* ...

* Fix compiler complaints

* Address linter complaints

* temp: update clang-format.yml

attempting to fix bad git diff

* Revert "temp: update clang-format.yml"

This reverts commit 02cda31.

* some light refactoring

* Fix bug in runElectionCampaign

* Add a test for leadership election terms

* Fix test comments and name

* Handle a corner case differently

* Remove rendundant comment

* Move to unified representation of Agency

* Rename files to make clearer what is supposed to to what

* Remove some no longer used files

* Add code for checking out target

* Add some stub code

* add more indexHints: `disableIndex` and `maxProjections` (#15446)

Co-authored-by: Michael Hackstein <michael@arangodb.com>

* fix pitfall for comdat folding (#15467)

Co-authored-by: Andrey Abramov <andrey@arangodb.com>

* small code cleanup (#15474)

* make it 2022 (#15466)

* [CINFRA-161] Follower State Transfer (#15352)

* Added log core to leader and follower.

* Rough sketch of snapshot transfer on followers.

* Added ILogLeader and ILogFollower interfaces.

* Optimized LogMultiplexer. Less copies of shared_ptrs.

* Added FakeReplicatedState.

* Fixing tests.

* Preparations for FollowerState tests.

* Renamed FakeFollower to FakeAbstractFollower.

* Added new FakeFollower.

* Moved interfaces to a separate header file.

* Moved LeaderStateManager and FollowerStateManager into sep. files.

* Completed first test run.

* Fixing use of temporary after expression.

* Code cleanup.

* Added missing include for mac.

* One more try for apple clang.

* Dropping std::totally_ordered because it is not supported by Jenkins apple-clang, using typename instead.

* Minor formatting

* Applied clang-format

* Reordered sources

* Fixed merge conflict

* Reformatted *.tpp files

* Switched to ParticipantResignedException

* Update arangod/Replication2/ReplicatedState/StateInterfaces.h

Co-authored-by: Alex Petenchea <alexandru.petenchea@arangodb.com>

* Use less special pointer.

Co-authored-by: apetenchea <alexandru.petenchea@arangodb.com>
Co-authored-by: Tobias Gödderz <tobias@arangodb.com>

* Move ReplicatedLog code into the correct place

* Make it build

* Fix compilation

* Use new code for supervision.

* add test

* Tests pass (or are deleted)

* Added test for setting a new leader.

* Sketch out checkReplicatedLog

* Stub out actions

* Bulk

* some more tests for Supervision functions

* Add some more harness code

* Remove LOG_DEVEL

* Added supervision trace if configured.

* all of it

* Fix supervision path

* Update participant flags

* Dictate leadership

* Added more tests for supervision.

* Resume all servers after each test.

* Added expected actions for changeLeader.

* More tests.

* Added experimental tests.

* LeaderElection

* Refactoring and cleanup of leader election

* Fix simple replication2 failover test

* Cleanup

* Remove stray console.log calls

* Fix testChangeLeader

* make more tests pass

* More tests 🎉

* Implement UpdateConfigAction

* Implement EvictLeader

* Added yet another test.

* An excluded server is not electible

* Remove redundant files

* Remove redundant files fixes

* Fixing unittests

* Fix embarassing crash

* Fix embarassing crash

* Enable Leader Replacement

* Fixing testCheckSimpleFailover. Sometimes leader was server[1].

* Added descriptions to tests. Exception handling supervision.

* Address comments

* remove stray file

* make clang-12 compile me again

* Fix a bug in testReplaceLeaderWithNewFollower

* Post errors to agency

* Add Supervision Errors

* removed targetConfig - discussed during review.

* make tests compile again

* Fix changing configuration through target

* be careful about leadership selection in Target

* Fix some tests

* Fix CMakeLists.txt

* make linter happy

* make linter happy

* Jslint.

* Fix shell tests

* Add a hack that fixes up when the user tries to add a log without participants

* clang-format

* Compiler nanny-ing

* More nanny

* clang format

* clang format

* MSVC complains that the defaulted constructor isn't defined

So we move it into the cpp file. Great good. So C++.

* Fix up some Agency Path cleanup fallout

* re-enable test

* Fix testLogStatus test

Co-authored-by: aMahanna <anthony.mahanna@gmail.com>
Co-authored-by: Jan <jsteemann@users.noreply.github.com>
Co-authored-by: Michael Hackstein <michael@arangodb.com>
Co-authored-by: Andrey Abramov <andrey@arangodb.com>
Co-authored-by: Lars Maier <lars@arangodb.com>
Co-authored-by: apetenchea <alexandru.petenchea@arangodb.com>
Co-authored-by: Tobias Gödderz <tobias@arangodb.com>