Ability to control "Become a <level> sponsor" links

[WhatsChrisDoing]

Extend the sponsor_levels array to include the number of sponsor slots at each level so that the "Become a sponsor" can be automatically excluded for levels that are full.

[bridgetkromhout]

Thanks for working on this, @yvovandoorn. I think this might be best configured like this:

sponsor_levels:
- id: platinum
label: Platinum
max: 3 # since Minneapolis already has 3, this would automatically remove the "become a..."
- id: gold
label: Gold
max: 12
- id: silver
label: Silver
number: # left blank which makes the number unlimited

And here's an optional but related possibility:

- id: host
  label: Host
  number: 1 # If one host sponsor is allowed, change "Host Sponsors" to instead display as "Host Sponsor".

Your option for turning off all "become a sponsor" messages on a city-wide basis is fine, but I suspect that the main uses of that would be "before the prospectus is done" and "when the conference is almost happening". So, an event-wide override like this might work:

sponsors_accepted: "yes"

I think it's fine for it to be a required field and could default to "no". Then people could turn it on when they're ready.

[bridgetkromhout]

Moving the discussion from #294 (comment), @yvovandoorn says:

The biggest challenge I've been having with Hugo (and thus my limits) is how the logic around how to compare sponsor.level vs sponsor_levels.max works.

Given this is my 4th day with Hugo (or Go in general) so far I've come this far:

      {{ else if ge var .max }}
         <div class = "sponsor-cta">
          <br>
       </div>

My struggles:

Is how to properly add up the levels set under sponsors.level against sponsor_levels.max.

Example

I have 4 sponsors:

 sponsors:
  - id: solvinity
    level: gold
  - id: stackstate
    level: gold
  - id: thoughtworks-products
    level: gold
 sponsor_levels:
  - id: gold
    label: Gold
    max: 2

How do I count up the id 'gold' being used 3x under sponsors to fire off against (greater than or equal to) under sponsor_levels.max:2. Feels like there is a loop in involved and the sysadmin in me to use unix commands to determine the comparison. Obviously not appropriate here.

[bridgetkromhout]

@pmoosh and @ksatirli are also probably interested in this.

[bridgetkromhout]

Solved by @jyee in #737. Thanks, Jason!