[FEATURE] Check the plugins installed before running provisioning

[owaiskazi19]

Is your feature request related to a problem?

Coming from 2nd task of #108.

Provision API runs a workflow Step which is nothing but a building block for a specific plugin. To execute the APIs of that plugin, it needs to be installed in the OS cluster or else flow framework plugin won't be able to do provisioning. We can't add all the plugins in extendedPlugins, that will create dependency on all the plugins even if their APIs are not required in any workflow step of the template.

What solution would you like?

There should be a mechanism to check the list of plugins installed and template should have a field called as plugins consisting of list of plugins required for a specific workflow. The first template validation should be to check if the plugins mentioned in the template are installed in the OS cluster.

What alternatives have you considered?

A clear and concise description of any alternative solutions or features you've considered.

Do you have any additional context?

Add any other context or screenshots about the feature request here.

[dbwiddis]

My preferred implementation:

1. add a field "required_plugins" (String array) to the workflow step JSON here.
2. when validating a plugin, iterate the steps (which we are already doing for validating input/output) and collect the strings from this entry, adding them to a Set as we go along
3. take this set and compare it to the list of installed plugins. See sample code here for obtaining installed plugins.

[joshpalis]

Closed by #290