add --external-url for alertmanager

[reAsOn2010]

What problem does this PR solve?

tiup deployed alertmanager creating alerts with unspecified external-url

What is changed and how it works?

the template generating alertmanager config

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Code changes

• Has exported function/method change
• Has exported variable/fields change
• Has interface methods change
• Has persistent data change

Side effects

• Possible performance regression
• Increased code complexity
• Breaking backward compatibility

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation

Release notes:

NONE

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• AstroProfundis

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[CLAassistant]

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[codecov-commenter]

Codecov Report

Merging #1608 (4ad54b7) into master (ebbeca0) will increase coverage by 24.69%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           master    #1608       +/-   ##
===========================================
+ Coverage   15.71%   40.40%   +24.69%     
===========================================
  Files         149      258      +109     
  Lines       15096    23073     +7977     
===========================================
+ Hits         2372     9323     +6951     
- Misses      12207    12391      +184     
- Partials      517     1359      +842     

Flag	Coverage Δ
cluster	39.35% <ø> (?)
dm	19.72% <ø> (?)
integrate	40.40% <ø> (+24.69%)	⬆️
tiup	?
unittest	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
pkg/repository/store/store.go	0.00% <0.00%> (-100.00%)	⬇️
pkg/repository/utils/hash.go	0.00% <0.00%> (-83.34%)	⬇️
pkg/repository/model/publish.go	0.00% <0.00%> (-83.34%)	⬇️
pkg/repository/store/local.go	0.00% <0.00%> (-82.61%)	⬇️
pkg/repository/progress.go	23.07% <0.00%> (-76.93%)	⬇️
pkg/telemetry/meta.go	0.00% <0.00%> (-67.40%)	⬇️
pkg/telemetry/telemetry.go	0.00% <0.00%> (-66.67%)	⬇️
pkg/repository/v1manifest/keys.go	5.33% <0.00%> (-58.67%)	⬇️
pkg/repository/merge_mirror.go	0.00% <0.00%> (-58.51%)	⬇️
pkg/utils/args.go	0.00% <0.00%> (-50.00%)	⬇️
... and 244 more

---

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[AstroProfundis]

Thank you for the contribute!

It would be better to add a ListenAddress for it, so that AlertManager could support VPC environment that listen IP and public access IP are different. (#1537)

But that's not necessarily a demand for this PR, I'd merge this, but it's also welcomed if you'd like to improve more on this.

[AstroProfundis]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: ec6ab84

[ti-chi-bot]

@reAsOn2010: Your PR was out of date, I have automatically updated it for you.

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