Document that Custom Build Strategy is disabled by default and how to enable it

[php-coder]

Inspired by the question on IRC:

tjololo> hi, is it possible to "enable" Custom Builds when you are using "oc cluster up". I'm trying to test a Custom Builder, but when I try to register the BuildConfig with custom as build strategy I get a error message saying: "build strategy Custom is not allowed."

It turns out that our documentation doesn't cover the current state of the Custom Build Strategy:

• nowhere is mentioned that this is disabled by default (and why)
• there is also no instructions how to enable it

I believe that at least the following places should be updated:

• https://docs.openshift.org/latest/dev_guide/builds/build_strategies.html#custom-strategy-options
• https://docs.openshift.org/latest/admin_guide/securing_builds.html#disabling-a-build-strategy-globally

Related issues:

• https://bugzilla.redhat.com/show_bug.cgi?id=1380462
• Don't give builds/custom access to system:authenticated by default origin#11411

CC @bparees @coreydaley

[bparees]

actually the doc clearly states that is it not disabled by default, so the question would be why is it disabled in oc cluster up? That is a question for @csrwng

By default, all users that can create builds are granted permission to use all build strategies (Docker, Source-to-Image, and Custom).

and i think this covers "instructions on how to enabled it":
https://docs.openshift.org/latest/admin_guide/securing_builds.html#restricting-build-strategies-to-a-user-globally

(but again we claim it's enabled by default, so if it's not we need to sort that out).

[csrwng]

Actually it should not be (enabled by default):
https://bugzilla.redhat.com/show_bug.cgi?id=1380462
openshift/origin#11411

[bparees]

assigning to @coreydaley then since the docs should have been updated when that change was put in.

[vrutkovs]

The docs are not updated yet, Securing builds by strategies states:

By default, all users that can create builds are granted permission to use all build strategies (Docker, Source-to-Image, and Custom).

[bparees]

@vrutkovs yes that's why this issue is still open....