Initial Bindings Delete API Implementation

[ralikio]

Description

Changes proposed in this pull request:

• injecting bindings storage into bind_delete endpoint,
• added instanceID to the delete storage method to uniquely identify a binding,
• delete method invocation in API endpoint,
• happy path test.

Related issue(s)

#284 #1198

[github-actions]

Add one of following labels

- kind/feature -> Use it when you want to submit a new feature

- kind/enhancement -> Use it when you modify or improve an existing feature

- kind/bug -> Use it when you fix a bug

[piotrmiskiewicz]

I think we need at least one small happy path binding deletion test in cmd/broker. It can be a next PR if you like

[ralikio]

I think we need at least one small happy path binding deletion test in cmd/broker. It can be a next PR if you like

@piotrmiskiewicz I intended bind_create_test.go to serve that purpose. However, the placement was incorrect. I have moved the file to broker package as well as switched in memory database to the one created in a container.