WIP(np): Notification Platform Example

[GabeVillalobos]

DO NOT MERGE: Example usages and very rough outline of potential notification platform code.

This is just here to illustrate what a potential solution could look like in the future, and to spur further conversation on the platform as a whole.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 48.58491% with 109 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...ple/real_world_example/user_invite_notification.py	10.86%	41 Missing :warning:
src/sentry/platform_example/notification.py	26.66%	22 Missing :warning:
...entry/notifications/template/test_template_base.py	21.73%	18 Missing :warning:
...c/sentry/platform_example/notification_provider.py	25.00%	12 Missing :warning:
src/sentry/platform_example/notification_target.py	16.66%	10 Missing :warning:
src/sentry/platform_example/template_base.py	91.80%	5 Missing :warning:
src/sentry/platform_example/notification_types.py	94.11%	1 Missing :warning:

:x: Your patch check has failed because the patch coverage (48.58%) is below the target coverage (50.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #87664       +/-   ##
===========================================
- Coverage   87.60%   46.26%   -41.34%     
===========================================
  Files       10324    10175      -149     
  Lines      586011   582176     -3835     
  Branches    22531    22531               
===========================================
- Hits       513378   269364   -244014     
- Misses      72211   312390   +240179     
  Partials      422      422               

[getsantry[bot]]

This pull request has gone three weeks without activity. In another week, I will close it.

But! If you comment or otherwise update it, I will reset the clock, and if you add the label WIP, I will leave it alone unless WIP is removed ... forever!

---

"A weed is but an unloved flower." ― Ella Wheeler Wilcox 🥀

[getsantry[bot]]

This issue has gone three weeks without activity. In another week, I will close it.

But! If you comment or otherwise update it, I will reset the clock, and if you remove the label Waiting for: Community, I will leave it alone ... forever!

---

"A weed is but an unloved flower." ― Ella Wheeler Wilcox 🥀

[getsantry[bot]]

This issue has gone three weeks without activity. In another week, I will close it.

But! If you comment or otherwise update it, I will reset the clock, and if you remove the label Waiting for: Community, I will leave it alone ... forever!

---

"A weed is but an unloved flower." ― Ella Wheeler Wilcox 🥀

[getsantry[bot]]

This issue has gone three weeks without activity. In another week, I will close it.

But! If you comment or otherwise update it, I will reset the clock, and if you remove the label Waiting for: Community, I will leave it alone ... forever!

---

"A weed is but an unloved flower." ― Ella Wheeler Wilcox 🥀

[getsantry[bot]]

This issue has gone three weeks without activity. In another week, I will close it.

But! If you comment or otherwise update it, I will reset the clock, and if you remove the label Waiting for: Community, I will leave it alone ... forever!

---

"A weed is but an unloved flower." ― Ella Wheeler Wilcox 🥀