Add Sort by Create Time to Fetch and Lock API

[psavidis]

Acceptance Criteria (Required on creation)

• Add the parameter to the Fetch and Lock API of External Tasks

  • Currently usePriority implementation defines the order statically to DESC. Change this to so that ordering can work both for ASC and DESC configuration for prioritising create-time in LIFO and FIFO orders.

• Implement Multi-Level Sorting By Considering Fields in the following order:

  • First priority is taken into account
  • In the equality scenario, create time will be used next.
  • The above order should be preserved for the Fetch and Lock API
  • For the External Task Query API, the multi-level sorting is handled consistently with all other Query APIs via the #orderBy… fluent builder pattern.

Hints

Links

External Tasks are Sorted By Creation Date

Breakdown

### Pull Requests
- [ ] https://github.com/camunda/camunda-bpm-platform/pull/3912

[psavidis]

Here is the Table with the different parameter combinations that can be passed to the Fetch and Lock API, along with their respective effective selection and config used:

useCreateTime	Direction	Effective Selection	Effective CreateTimeConfig
false	null	Ignore Sorting	EMPTY
false	DESC	Ignore Sorting	EMPTY
false	ASC	Ignore Sorting	EMPTY
true	null	Sort by Descending createTime (sensible default)	DESC
true	DESC	Sort by Descending createTime	DESC
true	ASC	Sort by Ascending createTime	ASC