Initialising Store front app using phoenix 1.4

[pkrawat1]

Why?

• In order to remove dependency with the front end app. We will be needing a store front app in umbrella that can also be used as the front app in phoenix.
• Also this will make it easy to run a multi tenant storefront with theme-able app.

This change addresses the need by:

• Adds a phoenix app named as store front in the umbrella apps dir.
• Updates cowboy deps to phoenix_cowboy.

Checklist

• I have read CONTRIBUTING.md.
• My code follows the style guidelines of this project.
• I have commented my code, particularly in hard-to-understand areas.
• My code does not generate any (new) credo and compile-time warnings.
• I have updated the documentation wherever necessary.
• I have added tests to cover my changes.

[codecov]

Codecov Report

Merging #467 into develop will increase coverage by 1.03%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop     #467      +/-   ##
===========================================
+ Coverage    78.98%   80.01%   +1.03%     
===========================================
  Files          176      177       +1     
  Lines         2208     2287      +79     
===========================================
+ Hits          1744     1830      +86     
+ Misses         464      457       -7

Impacted Files	Coverage Δ
apps/snitch_core/lib/core/data/model/zone/zone.ex	59.52% <0%> (-6.27%)	⬇️
...s/snitch_core/lib/core/data/schema/tax/tax_zone.ex	100% <0%> (ø)	⬆️
apps/snitch_core/lib/core/data/schema/zone/zone.ex	100% <0%> (ø)	⬆️
...ps/snitch_core/lib/core/data/model/tax/tax_zone.ex	100% <0%> (ø)	⬆️
.../schema/shipping_rules/shipping_rule_identifier.ex	100% <0%> (ø)
apps/snitch_core/lib/core/domain/tax.ex	97.87% <0%> (+1.64%)	⬆️
.../snitch_core/lib/core/data/model/product_review.ex	96.77% <0%> (+3.22%)	⬆️
..._core/lib/core/data/model/general_configuration.ex	72.72% <0%> (+9.09%)	⬆️
...core/lib/core/data/schema/review/product_review.ex	100% <0%> (+25%)	⬆️
...snitch_core/lib/core/data/model/shipping_method.ex	100% <0%> (+30%)	⬆️
... and 3 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 9f5b95a...f930592. Read the comment docs.