Improve performance of dashboard

[lunny]

Will resolve #3367

[tonivj5]

Is it ready to review? 👍 I'm having a lot of problems because of that 😢

[lunny]

@xxxTonixxx I will fix the tests failure.

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@49ea6e0). Click here to learn what that means.
The diff coverage is 43.52%.

@@            Coverage Diff            @@
##             master    #4977   +/-   ##
=========================================
  Coverage          ?   37.54%           
=========================================
  Files             ?      320           
  Lines             ?    47144           
  Branches          ?        0           
=========================================
  Hits              ?    17702           
  Misses            ?    26900           
  Partials          ?     2542

Impacted Files	Coverage Δ
routers/api/v1/repo/pull.go	17.13% <0%> (ø)
models/issue_mail.go	12% <0%> (ø)
models/issue_tracked_time.go	67.56% <0%> (ø)
models/issue_stopwatch.go	71.05% <0%> (ø)
models/mail.go	1.72% <0%> (ø)
routers/repo/issue.go	36.88% <10%> (ø)
routers/user/home.go	41.88% <100%> (ø)
models/update.go	31.65% <100%> (ø)
routers/api/v1/repo/issue_comment.go	56.25% <11.11%> (ø)
routers/repo/pull.go	33.58% <19.04%> (ø)
... and 7 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 49ea6e0...3b4f795. Read the comment docs.