User may customise heat capacity per connection

[antw]

This PR adds an input on the testing ground "general" form allowing the visitor to customise the central heat buffer volume per heat-connection. Defaults to nil/NULL, which in turn will default to 10kWh in Network::Builders::Heat (so that if we change the default in the future, older LESes won't be stuck with an out-of-date value).

I think this field would be more at home on the "Heat source list" tab, but I'm not sure if that's possible? All the fields on that page relate to the heat source list, while this is a column on the testing_grounds table. I think this is not a deal-breaker.

@grdw Can you take a look at this when you have the time? Thanks!

Ping @ChaelKruip

[grdw]

I have no idea how to properly test this. It doesn't cause any errors when changing the number, saving works, all the basics still function + the specs succeed 👍 . I don't see any difference in my heat calculation but that can be because I don't know exactly what to look for.

[grdw]

I think this field would be more at home on the "Heat source list" tab, but I'm not sure if that's possible?

It could be. If you edit the testing_grounds/edit.html.haml and add another form to the heat source list pane it will probably work 👍.

[antw]

I have no idea how to properly test this.

We don't have specs for the network calculation, so you'll have to take my word for it. 😆 Here are some screenshots from a local LES:

0kWh per connection (no buffering occurs):

No value set (defaults to 10kWh):

100kWh per connection:

[grdw]

so you'll have to take my word for it.

expect(true).to eq(true)

[antw]

expect(true).to eq(true)

So, about that... 😱

(my bad!)