Default iframe set via env var

[Alexander-Da-Great]

Checked for duplicates

Yes - I've already checked

Alternatives considered

No - I haven't considered

Related problems

No response

Describe the feature request

I want a way to set the default iframe url for the aerie UI when started - without having to define a new view. Currently this is hard coded as 'https://eyes.nasa.gov/apps/mars2020/#/home'.

[joswig]

action to discuss if this is the preferred mechanism for customizing