Updating Slack Notification not working by API

Summary

We are trying to update service slack notification settings through the API v4 and it always come back as the same entity before we PUT our changes. Like shown in: https://docs.gitlab.com/ce/api/services.html#slack-notifications

Are we doing something incorrectly?

Steps to reproduce

Have a slack notification user set to something else than "test" we used "git" as username.

Update it through API https://gitlab.host.com/api/v4/projects/156/services/slack

What is the current bug behavior?

Run this request: curl -X PUT --header "Content-Type: application/json" --header "PRIVATE-TOKEN: my_token" --data '{"webhook":"https://hooks.slack.com/services/my/slack/hook","username":"test"}' https://gitlab.host.com/api/v4/projects/156/services/slack

Response not updated:

{"id":1851,"title":"Slack notifications","created_at":"2017-05-15T17:20:37.998-03:00","updated_at":"2017-05-16T13:17:54.061-03:00","active":true,"push_events":true,"issues_events":true,"merge_requests_events":true,"tag_push_events":true,"note_events":true,"pipeline_events":true,"job_events":false,"properties":{"webhook":"https://hooks.slack.com/services/my/slack/hook","username":"git","notify_only_broken_pipelines":"0","notify_only_default_branch":"0","push_channel":"#testing","issue_channel":"#testing","confidential_issue_channel":"#testing","merge_request_channel":"#testing","note_channel":"","tag_push_channel":"#testing","pipeline_channel":"","wiki_page_channel":"#testing"}}

What is the expected correct behavior?

We expected an update json like:

{"id":1851,"title":"Slack notifications","created_at":"2017-05-15T17:20:37.998-03:00","updated_at":"2017-05-16T13:17:54.061-03:00","active":true,"push_events":true,"issues_events":true,"merge_requests_events":true,"tag_push_events":true,"note_events":true,"pipeline_events":true,"job_events":false,"properties":{"webhook":"https://hooks.slack.com/services/my/slack/hook","username":"test","notify_only_broken_pipelines":"0","notify_only_default_branch":"0","push_channel":"#testing","issue_channel":"#testing","confidential_issue_channel":"#testing","merge_request_channel":"#testing","note_channel":"","tag_push_channel":"#testing","pipeline_channel":"","wiki_page_channel":"#testing"}}

Relevant logs and/or screenshots

We did not found any error or warning messages related to this. Only the correct access_log with PUT method.

Results of GitLab environment info

Expand for output related to GitLab environment info

System information
System:		Ubuntu 14.04
Current User:	git
Using RVM:	no
Ruby Version:	2.3.3p222
Gem Version:	2.6.6
Bundler Version:1.13.7
Rake Version:	10.5.0
Redis Version:	3.2.5
Git Version:	2.11.1
Sidekiq Version:4.2.7
GitLab information
Version:	9.1.4
Revision:	fed799a
Directory:	/opt/gitlab/embedded/service/gitlab-rails
DB Adapter:	postgresql
URL:		http://gitlab.host.com
HTTP Clone URL:	http://gitlab.host.com/some-group/some-project.git
SSH Clone URL:	git@gitlab.host.com:some-group/some-project.git
Using LDAP:	yes
Using Omniauth:	no
GitLab Shell
Version:	5.0.2
Repository storage paths:

• default: /var/opt/gitlab/git-data/repositories Hooks: /opt/gitlab/embedded/service/gitlab-shell/hooks Git: /opt/gitlab/embedded/bin/git

Results of GitLab application Check

Expand for output related to the GitLab application check

Checking GitLab Shell ...
GitLab Shell version >= 5.0.2 ? ... OK (5.0.2)
Repo base directory exists?
default... yes
Repo storage directories are symlinks?
default... no
Repo paths owned by git:git?
default... yes
Repo paths access is drwxrws---?
default... yes
hooks directories in repos are links: ...
4/1 ... ok
10/4 ... ok
3/5 ... ok
12/14 ... ok
12/15 ... ok
12/16 ... ok
3/18 ... ok
10/19 ... ok
16/23 ... ok
12/24 ... ok
16/27 ... ok
17/30 ... ok
17/31 ... ok
18/32 ... ok
18/33 ... ok
18/34 ... ok
18/35 ... ok
20/43 ... ok
4/44 ... ok
16/45 ... ok
3/51 ... ok
23/52 ... ok
2/58 ... repository is empty
20/60 ... ok
3/61 ... ok
3/62 ... ok
24/63 ... ok
27/64 ... ok
27/65 ... ok
27/66 ... ok
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27/68 ... ok
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15/70 ... ok
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2/114 ... ok
47/115 ... ok
27/116 ... ok
18/117 ... ok
3/118 ... repository is empty
48/120 ... ok
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48/123 ... ok
48/124 ... ok
2/125 ... ok
12/126 ... ok
48/127 ... ok
48/128 ... ok
48/129 ... ok
4/130 ... ok
47/131 ... repository is empty
4/132 ... ok
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48/135 ... ok
40/136 ... ok
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51/138 ... ok
52/139 ... ok
4/140 ... ok
4/141 ... ok
4/142 ... ok
4/143 ... repository is empty
48/144 ... ok
45/145 ... ok
2/148 ... repository is empty
12/149 ... repository is empty
54/150 ... ok
55/151 ... ok
54/152 ... ok
3/153 ... ok
48/154 ... ok
57/156 ... repository is empty
Running /opt/gitlab/embedded/service/gitlab-shell/bin/check
Check GitLab API access: OK
Access to /var/opt/gitlab/.ssh/authorized_keys: OK
Send ping to redis server: OK
gitlab-shell self-check successful
Checking GitLab Shell ... Finished
Checking Sidekiq ...
Running? ... yes
Number of Sidekiq processes ... 1
Checking Sidekiq ... Finished
Checking Reply by email ...
Reply by email is disabled in config/gitlab.yml
Checking Reply by email ... Finished
Checking LDAP ...
Server: ldapmain
LDAP authentication... Success
LDAP users with access to your GitLab server (only showing the first 100 results)
{ log removed }
Checking LDAP ... Finished
Checking GitLab ...
Git configured with autocrlf=input? ... yes
Database config exists? ... yes
All migrations up? ... yes
Database contains orphaned GroupMembers? ... no
GitLab config exists? ... yes
GitLab config outdated? ... no
Log directory writable? ... yes
Tmp directory writable? ... yes
Uploads directory setup correctly? ... yes
Init script exists? ... skipped (omnibus-gitlab has no init script)
Init script up-to-date? ... skipped (omnibus-gitlab has no init script)
projects have namespace: ...
4/1 ... yes
10/4 ... yes
3/5 ... yes
12/14 ... yes
12/15 ... yes
12/16 ... yes
3/18 ... yes
10/19 ... yes
16/23 ... yes
12/24 ... yes
16/27 ... yes
17/30 ... yes
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18/35 ... yes
20/43 ... yes
4/44 ... yes
16/45 ... yes
3/51 ... yes
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2/58 ... yes
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3/61 ... yes
3/62 ... yes
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48/129 ... yes
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48/137 ... yes
51/138 ... yes
52/139 ... yes
4/140 ... yes
4/141 ... yes
4/142 ... yes
4/143 ... yes
48/144 ... yes
45/145 ... yes
2/148 ... yes
12/149 ... yes
54/150 ... yes
55/151 ... yes
54/152 ... yes
3/153 ... yes
48/154 ... yes
57/156 ... yes
Redis version >= 2.8.0? ... yes
Ruby version >= 2.1.0 ? ... yes (2.3.3)
Your git bin path is "/opt/gitlab/embedded/bin/git"
Git version >= 2.7.3 ? ... yes (2.11.1)
Active users: 20
Checking GitLab ... Finished