Postgres table in which data exists can't be upsert unless "key" is specified in the config when creating

[uchennakevinm1]

Postgres table in which data exists can't be upsert unless "key" is specified in the config when creating  Postgres Destination connector (request: /v1/connectors). Even if the "key" field is present in the metadata
Steps to reproduce

1. There is a table with data with the  primary "key" in Postgres
2. Create a new pipeline
3. Create Postgres destination connector with configs
   "settings": {
   "url": "postgresql://postgres:postgres@localhost:5432/postgres",
   table: "",
   "key": ""
   }
4. Create Source connector that transfers the "key" in metadata (For example, Postgres or Snowflake Source)
5. Run the pipeline -> the system is trying to transfer data by "key" which already exists
   Actual result: data isn't transferred to the Postgres table
   Expected result: The data should be updated by "key" from the metadata.

2022-05-12T13:56:39+00:00 ERR node stopped error="node 9873f4b8-61d7-483e-8b24-a52f12395ad0-acker stopped with error: error receiving ack: ERROR: duplicate key value violates unique constraint "table2_pkey" (SQLSTATE 23505)" component=pipeline.Service node_id=9873f4b8-61d7-483e-8b24-a52f12395ad0-acker stack=[{"file":"/Users/serhii/conduit/pkg/pipeline/lifecycle.go","func":"github.com/conduitio/conduit/pkg/pipeline.(*Service.runPipeline.func1","line":387},{"file":"/Users/serhii/conduit/pkg/connector/destination.go","func":"github.com/conduitio/conduit/pkg/connector.(*destination.Ack","line":194},{"file":"/Users/serhii/conduit/pkg/plugin/builtin/v1/destination.go","func":"github.com/conduitio/conduit/pkg/plugin/builtin/v1.(*destinationPluginAdapter.Ack","line":137}]

[uchennakevinm1]

related to issues #58