NetBox 2.9 support

[mzbroch]

This PR introduces the support of NetBox 2.9 into the ntc-netbox-plugin-onboarding project.

The goal is to provide support for two NetBox releases by the plugin: 2.8 and 2.9. Due to significant Permission related changes in NetBox 2.9, onboardingtask views needed to be modified.

The following changes are a part of this single commit :

• filters.py - duplicated site_id
• search fixed in filters
• OnboardingTaskFeedCSVForm now inherits from CSVModelForm (fixes #88 )
• conditional (if 2.9) model attribute in OnboardingTask model
• fixed the reverse names to follow NetBox convention
• added release statements in release.py
• dedicated view for a single onboarding task
• Onboarding Task tables now show Link Column for Onboarding Task id
• replaced existing view's unit tests with NetBox unit tests, still separated for NetBox 2.8 and 2.9
• conditionals in unit tests (2.8 or 2.9)
• conditionals in view classes (2.8 or 2.9)

[hyudra]

Hello,

Is this version merged for pip library? I still get error message 'Direct assignment to the reverse side of a related set is prohibited. Use interface.set() instead.'

[dgarros]

@hyudra no it's not available on pypi yet, out goal is to have a beta version for 2.9 out sometime this week but it won't be production ready

[hyudra]

Noted with thanks. I'll looking forward to it :).