Custom base URL support, configurable by environment variable

[conroy-cheers]

No description provided.

[freyta]

I'm not quite sure what the point of this is? I don't know what use this would be for the majority of people. Excuse my ignorance.

[NGPriest]

I would agree with @freyta with this PR...

[conroy-cheers]

Use case is when running it behind a proxy, at e.g. my.domain.com/proxy_path/ - by configuring the app to use /proxy_path/ as the base URL, all the links and static files will work properly. Much cleaner than getting the proxy server to rewrite URLs in the HTML.
This is a fairly common option for web apps - I needed it for my usage. Just thought it might be useful for others too 😊

[beaudeanadams]

This may be somewhat related to #47 iirc
However, I feel it should be done in line with the current coding style (i.e. not changing app to app_blueprint)

[conroy-cheers]

I did some (admittedly quick) research and from what I saw, using a blueprint seemed to be the cleanest solution, as it functions similarly to the default app but allows for configurable base URL as an option.

I’m open to suggestions though - I’m far from an expert on Flask. If there’s another method you’d prefer, I could take a look at implementing it instead.

[NGPriest]

Do they really have honeypots? :S

I mean, if someone happened to live locally and locked in the "special" price, do they expect to get banned?