Prometheus endpoint

[gaydin]

I want to try to finish the task #2751, initial commits are based on #678

I need help on several issues:
1. How can l make an authorization token?
It is necessary to use a token in app.ini and make it accessible from the section /admin?
Is need to make token in modules/gererate and save in configuration,If the token doesn't exist in configuration?

2. Do I need to add "metrics" in a reservedUsernames?
3. How can l correct dependencies?
This PR is build successfully just if update it manually github.com/golang/protobuf

sorry for my bad english :)

[sapk]

At first sight, I would say yes to all the question.

For the deps, does dep ensure -update github.com/golang/protobuf solve the problem ?

[codecov-io]

Codecov Report

Merging #5256 into master will decrease coverage by 0.22%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #5256      +/-   ##
==========================================
- Coverage    37.6%   37.37%   -0.23%     
==========================================
  Files         310      312       +2     
  Lines       46054    46327     +273     
==========================================
- Hits        17320    17317       -3     
- Misses      26254    26527     +273     
- Partials     2480     2483       +3

Impacted Files	Coverage Δ
models/user.go	44.64% <ø> (ø)	⬆️
routers/metrics.go	0% <0%> (ø)
routers/routes/routes.go	85.45% <0%> (-0.8%)	⬇️
modules/metrics/collector.go	0% <0%> (ø)
modules/setting/setting.go	48.18% <0%> (-0.13%)	⬇️
modules/process/manager.go	76.81% <0%> (-4.35%)	⬇️

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[gaydin]

For the deps, does dep ensure -update github.com/golang/protobuf solve the problem ?

Yes it helped. thank

[gaydin]

Bad idea to put metrics handler in a separate file?

By default metrics are disabled. If enable metrics will be available /metrics without authorization. But you can also add a token, then access to /metrics will be available only with a token.

[techknowlogick]

I think having it in separate file is best, because it is a unique area (just like how the api is split off into different files).

[techknowlogick]

Maintainers note: Dismissing @lunny's review as requested change has been made, and there are 4 other positive reviews.

change has been made (see my comment above)