feat: coupon code for bounty creation fee

[thelostone-mc]

Description

• added Coupon model
• admin can create coupon with expiry date and share bounty
  creation URL
• bounty creation will load updated fee if coupon hasn't expired
• bounty metadata is updated to keep track if bounty used a coupon
• updated web3 not defined error message
• refactored css

How it would work

1. admin created new coupon in admin with the following information
   • coupon code
   • fee % (should be between 0 to 100)
   • expiry date
2. Upon creation the admin will be able to view the URL they can share AS SHOWN HERE which will be something like http://gitcoin.co/funding/new?coupon=FREE-50
3. Once funder receives the URL the new fee will be applied.
4. For reporting purpose bounties which have been funded with a coupon will have that information
   in the bounty on admin AS SHOWN HERE

DEMO: https://embed.vidyard.com/share/rzwbLjVvVHbeVuzCbdVUuD?

Fixes: #4497

[codecov]

Codecov Report

Merging #4237 into master will increase coverage by 0.06%.
The diff coverage is 43.75%.

@@            Coverage Diff             @@
##           master    #4237      +/-   ##
==========================================
+ Coverage   30.12%   30.19%   +0.06%     
==========================================
  Files         210      209       -1     
  Lines       16911    16917       +6     
  Branches     2284     2282       -2     
==========================================
+ Hits         5095     5108      +13     
+ Misses      11619    11612       -7     
  Partials      197      197

Impacted Files	Coverage Δ
app/dashboard/views.py	14.2% <0%> (-0.08%)	⬇️
app/dashboard/helpers.py	13.99% <0%> (-0.19%)	⬇️
app/dashboard/admin.py	65.92% <58.33%> (-0.75%)	⬇️
app/dashboard/models.py	56.78% <87.5%> (+0.15%)	⬆️
app/retail/views.py	28.84% <0%> (-0.29%)	⬇️
...p/dashboard/management/commands/sync_es_profile.py

---

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[codecov]

Codecov Report

Merging #4237 into master will decrease coverage by 0.01%.
The diff coverage is 43.75%.

@@            Coverage Diff            @@
##           master   #4237      +/-   ##
=========================================
- Coverage   30.11%   30.1%   -0.02%     
=========================================
  Files         210     210              
  Lines       16919   16950      +31     
  Branches     2286    2290       +4     
=========================================
+ Hits         5095    5102       +7     
- Misses      11626   11650      +24     
  Partials      198     198

Impacted Files	Coverage Δ
app/dashboard/views.py	14.2% <0%> (-0.08%)	⬇️
app/dashboard/helpers.py	13.99% <0%> (-0.19%)	⬇️
app/dashboard/admin.py	65.92% <58.33%> (-0.75%)	⬇️
app/dashboard/models.py	56.78% <87.5%> (+0.15%)	⬆️
app/dashboard/embed.py	28.16% <0%> (-3.45%)	⬇️

---

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[frankchen07]

qq - for expired coupons, the functionality looks solid (becaue the coupon is expired they have to pay full price), but it doesn’t actually let the user know “hey the coupon is expired” (like a red text box) do you think this is necessary? like a “if now() > coupon expiration date, and they’re using the link, so a box that says the coupon is expired”

[octavioamu]

amazing

[danlipert]

nice!