Georgios Katsikas authored Oct 06, 2022 and famelis committed Dec 12, 2022

Signed-off-by: Georgios P. Katsikas <gkatsikas@ubitech.eu>

- migrated to new ServiceHandler API
- added missing __init__.py file

- Renamed DependencyResolver to TaskScheduler
- Enhanced TaskScheduler with an extensible Task API framework and extensible dependency resolver
- Created TaskExecutor providing an extensible task execution environment
- Removed in-memory database; now is stateless and interrogates/updates Context when needed
- Extended gRPC servicer to use new TaskScheduler
- Removed unneeded files and re-organized helper methods
- Extended ServiceHandlerAPI; now SetEndpoint/DeleteEndpoint enables to configure/deconfigure a connection
- Moved ServiceHandlerFactory-related methods to the appropriate file
- Created ConnectionExpander to resolve from ERO-like paths to lists of links
- Created basic tasks: ServiceSetState, ServiceDelete, ConnectionConfigure, ConnectionDeconfigure
- Added skeleton for L2NMEmulatedHandler (to be adapted, now is a copy of L3NM one)

Merge in XRCA/teraflow from vhallivu/XR_DRIVER_EMULATE_ENDPOINTS to xr_development

Squashed commit of the following:

commit da5b46937d8f0dd87f535e3d736dc1d9e2043e94
Author: Ville Hallivuori <VHallivuori@infinera.com>
Date:   Mon Aug 8 15:21:16 2022 +0300

    Updates to emulation

commit b9d9e566f4622f85767c85b72494fbb33896de60
Author: Ville Hallivuori <VHallivuori@infinera.com>
Date:   Mon Aug 8 13:49:55 2022 +0300

    Add XR constellation icon for topology

commit 6d24a643f11ecb684043332500c2ee8b2768e900
Author: Ville Hallivuori <VHallivuori@infinera.com>
Date:   Mon Aug 8 12:56:16 2022 +0300

    Improved XR service creation stubs

commit 7d31fd2ecc67848368e2d0eddb616faa6115128d
Author: Ville Hallivuori <VHallivuori@infinera.com>
Date:   Mon Aug 8 08:07:10 2022 +0300

    Eulation for XrDriver endpoints

- implemented skeleton for L2VPN service handlers for emulated devices

First functional version of Service with Service Handler for L3NM-Emulated services using Emulated Devices