* Initial commit of rest high level exposure of cancel task
* fix javadocs
* address some code review comments
* update branch to use tasks namespace instead of cluster
* High-level client: list tasks failure to not lose nodeId
This commit reworks testing for `ListTasksResponse` so that random
fields insertion can be tested and xcontent equivalence can be checked
too. Proper exclusions need to be configured, and failures need to be
tested separately. This helped finding a little problem, whenever there
is a node failure returned, the nodeId was lost as it was never printed
out as part of the exception toXContent.
* added comment
* merge from master
* re-work CancelTasksResponseTests to separate XContent failure cases from non-failure cases
* remove duplication of logic in parser creation
* code review changes
* refactor TasksClient to support RequestOptions
* add tests for parent task id
* address final PR review comments, mostly formatting and such
Our API spec define the tasks API as e.g. tasks.list, meaning that they belong to their own namespace. This commit moves them from the cluster namespace to their own namespace.
Relates to #29546
Paul Sanwald
Luca Cavanna