refactor: support passing plugins response handlers and middlware

[chrisvogt]

This PR coincides with personal-api/plugin-instagram#4, and adds support for passing the Instagram plugin the success handlers, error handlers, and an Express middleware. My initial use case for this is to pass the cache middleware to the route attached by the plugin,

[codecov]

Codecov Report

Merging #30 into master will decrease coverage by 34.1%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           master      #30       +/-   ##
===========================================
- Coverage     100%   65.89%   -34.11%     
===========================================
  Files          19       20        +1     
  Lines         175      173        -2     
===========================================
- Hits          175      114       -61     
- Misses          0       59       +59

Impacted Files	Coverage Δ
src/utils/getCache.js	100% <100%> (ø)
src/api/base.js	100% <100%> (ø)	⬆️
src/routes.js	100% <100%> (ø)	⬆️
src/database/services.js	22.22% <0%> (-77.78%)	⬇️
src/controllers/projects.js	40% <0%> (-60%)	⬇️
src/controllers/composite.js	42.85% <0%> (-57.15%)	⬇️
src/helpers/joinRepoToProject.js	55.55% <0%> (-44.45%)	⬇️
src/controllers/metas.js	55.55% <0%> (-44.45%)	⬇️
src/controllers/repositories.js	55.55% <0%> (-44.45%)	⬇️
src/controllers/profiles.js	55.55% <0%> (-44.45%)	⬇️
... 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 541ee08...1ac6b91. Read the comment docs.

[chrisvogt]

Example showing Instagram data being cached:

Before

After

[chrisvogt]

This worked perfectly! Each call to the Instagram endpoint had been taking ~900ms. Now cached responses are returning in ~30ms.

Before

After