Feature: Enhance OPC-UA adapter to be more customizable and to perform additional functions

[WashingtonKK]

Is your feature request related to a problem? Please describe.

No issue

Describe the feature you are requesting, as well as the possible use case(s) for it.

Currently, when a successful subscription is made to the opc-ua server by the opc-ua adapter, the subscription details are stored such that the subscription will always be maintained even when the adapter is restarted or the thing is disconnected from the channel in magistrala.

This is a proposal that when the thing is disconnected from the channel, there needs to be an option to disconnect the adapter from the server so that the adapter will not keep consuming data from the opc-ua server.

Additionally, we can have the adapter such that it exposes another endpoint apart from /browse which can be used to perform these operations, say to establish a connection to a server, disconnect from a server.

Indicate the importance of this feature to you.

Nice-to-have

Anything else?

No response

[WashingtonKK]

Also update the adapter to the latest version of gopcua library.

[WashingtonKK]

Additional proposal to add the following endpoints:

1. /subscribe to give provision for manual subscription to a server.
2. /unsubscribe to allow a user to manually cancel a subscription to a sever.