Multi-tenant UI improvements

[bzoel]

While testing out the multi-tenant support, I found myself having to constantly select the tenant I am working in each time I added a device or viewed a page. I would suggest that there be a way to select the tenant you're working in, for example:

When I want to work on something for "Company A", I could go to a 'Select Tenant' box at the top of the page and select Company A. While this selection is in place, additions and views could be generated as though I was using NetBox for only Company A (without multi-tenant support). I could then change this global selection to "Company B", and the process would be similar.

I'm not sure if this is totally clear, but if you have used Cisco Prime, it functions similarly when you use mutli-tenant support. Let me know if I need to clarify further, or if others feel this wouldn't make sense in their case.

[bzoel]

Maybe this could also be extended to allow specific users access to only specific tenants... although that is probably a bit more involved.

[traveler3468]

In total agreement that this would be a necessary feature! My org needs NetBox and will most likely still use it (still in POC phase preping for presentation). Having access restricted to specific tenants or sites would be massively awesome!

@jeremystretch btw: Fantastic work on putting this together! I know how much work goes into something like this and you've done a fantastic job!

[jeremystretch]

Seems like this is probably better covered by #554. Closing this out.