Add end point to list all connections

[congwang09]

Resolves: https://github.com/atlanticwave-sdx/sdx-controller/issues/239

Add end point to list all connections. Also use ["topologies", "connections", "domains", "links"] collections to store different types of data. So we can grab all data from connections collection to get all connections.

[coveralls]

Pull Request Test Coverage Report for Build 8987515069

Details

• 19 of 32 (59.38%) changed or added relevant lines in 5 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.07%) to 51.117%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
sdx_controller/messaging/rpc_queue_consumer.py	3	4	75.0%
sdx_controller/utils/db_utils.py	12	15	80.0%
sdx_controller/controllers/connection_controller.py	3	7	42.86%
sdx_controller/handlers/lc_message_handler.py	0	5	0.0%
<!--	Total:	19	32	59.38%	-->

Files with Coverage Reduction	New Missed Lines	%
sdx_controller/handlers/lc_message_handler.py	1	22.22%
<!--	Total:	1		-->

Totals
Change from base Build 8879267390:	0.07%
Covered Lines:	714
Relevant Lines:	1429

---

💛 - Coveralls

[congwang09]

looks fine except for one thing: the return of the /connections Get

The function returns a list of connections, (1) would this list be serialized correctly in response? (2) in swagger.yaml, the schema is specified to use the '#/components/schemas/connection', which is a single connection object.

Maybe it is ok, just check what the test shows.

Yes, that's a great find. the return should be a list of connections. Updated.