This allows clients to implement custom operation more easily.

* Add support for link type between issues

Fixes #847

* Create AbstractIssue

* Add repository submodules api

Fixes #921

* Fix unit test

Fixes #883

Fixes #887

Fixes #936

Co-authored-by: Ипполитов Вадим Дмитриевич <vippolitov@poidem.ru>

Co-authored-by: Jérémie Bresson <dev@jmini.fr>

Fixes #849

Co-authored-by: Michael Me Jaeger <michael.me.jaeger@deutschebahn.com>

Co-authored-by: Michael Fitoussi <16884890+mifitous@users.noreply.github.com>

* Added ReleaseLinks API (#639)

* Deprecate the "external" attribute in Link

* Add tests

* Rename to ReleaseLinksApi and add the getter in GitLabApi

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Co-authored-by: Jeremie Bresson <jeremie.bresson@unblu.com>

* Added hook and fetch capabilities

* Fix tests

* Remove superfluous formatting

Fixes #931

Co-authored-by: Jeremie Bresson <jeremie.bresson@unblu.com>

* Add getDescendantGroups() methods to GroupApi

* Update javadoc

* Fix typo in method name

* Fix typo in the javadoc

Fixes #889

Add iterationTitle in IssueFilter for filtration issues
by this field

Co-authored-by: Усачев Дмитрий Дмитриевич <92usachevdd@region.cbr.ru>

* feat(scheduled-pipeline): makes scheduled pipelines runnable

* Update src/main/java/org/gitlab4j/api/PipelineApi.java

Co-authored-by: Jérémie Bresson <dev@jmini.fr>

* fix(scheduled-pipeline): change post()-call

* Update src/main/java/org/gitlab4j/api/PipelineApi.java

Co-authored-by: Jérémie Bresson <dev@jmini.fr>

* Add missing import

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Co-authored-by: Jérémie Bresson <dev@jmini.fr>
Co-authored-by: Jeremie Bresson <jeremie.bresson@unblu.com>
Co-authored-by: Ruben Vitt <dev@rubeen.one>

* Add ExternalStatusCheckApi

Fixes #919

* Add ExternalStatusCheckEvent

* Fix javadoc

There was not chance of throwing checked exception GitLabApiException  from given three methods. I have removed them to make user code using given methods easier to read.

Co-authored-by: Erkan <erkanerkisi>

Co-authored-by: Jérémie Bresson <dev@jmini.fr>

change projectIdOrPath as Object type

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Co-authored-by: jason <jason.irwin@idoxgroup.com>

Co-authored-by: Matteo Marras <matteo.marras@ti8m.ch>

Co-authored-by: Vladimir Krumov <vladimir.krumov@paysafe.com>