Implement optional embedding of custom RPMs in the RHEL4Edge image

[ggiguash]

Implement optional embedding of custom RPMs in the RHEL4Edge image to allow MicroShift container image delivery as part of the ISO.

The following changes were implemented:

• Added optional -custom_rpms command line to the image-builder/build.sh script
• Separate the ISO creation and installation docs from the developer documentation
• Added "Install MicroShift on RHEL for Edge" link to the User Documentation in the top-level README
• Added "mock" install and configuration for the devenv
• Updated docs for creating Offline Containers RPMs
• Updated docs on testing Offline Containers on a VM without the Internet access

USHIFT-112

[openshift-ci]

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[ggiguash]

/assign @dhellmann

[dhellmann]

/approve

I verified that using the build script in #748 the instructions work to build the RPM with the containers.

[openshift-ci]

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[fzdarsky]

@ggiguash, is rhel4edge_iso.md meant to be user documentation or documentation for developers of MicroShift?

I understood USHIFT-112 to be about user documentation and the main README links to there from the user documentation section, but the way rhel4edge_iso.md is written and the fact that it uses the scripts in script/image-builder suggests it's actually MicroShift developer documentation.

[ggiguash]

@fzdarsky, Yes, it's supposed to be a "user doc" in a way that explains the user how to use the existing tools to build their own custom procedures. I did not know there was a convention on what scripts users should run from the tree. If so, we can move some scripts around.
P.S. If we decide moving scripts, I would try it in a separate task/PR for the whole tree, not just the image-builder.

[ggiguash]

If this current documentation is more developer-oriented, maybe we just need to move it to the developer section in the top-level README.md

[fzdarsky]

@fzdarsky, Yes, it's supposed to be a "user doc" in a way that explains the user how to use the existing tools to build their own custom procedures. I did not know there was a convention on what scripts users should run from the tree. If so, we can move some scripts around. P.S. If we decide moving scripts, I would try it in a separate task/PR for the whole tree, not just the image-builder.

I'd say we need both user documentation and developer documentation:

1. The user documentation should IMO focus on consuming MicroShift RPMs as-is and describe both how to install MicroShift RPMs on non-rpm-ostree systems as well as how to embed MicroShift into an rpm-ostree image and how to make MicroShift and workloads "offline available". When doing so, it should not be us prescribing how to build images, but instead we'd simply refer to the RHEL documentation and describe how to do the MicroShift-specific stuff (e.g. "You need to enable repo X, add Y to your blueprint, Z to your kickstart. If you want to add containers, to this. If you want to package your apps into an RPM to that.")
2. The developer documentation (which is for ourselves) should be very prescriptive / reproducible in contrast. This is where we'd want the scripts in script/image-builder.

[ggiguash]

Moved the rhel4edge_iso.md document to the dev section in the top-level README and adjusted its intro to denote the dev audience.

[fzdarsky]

Moved the rhel4edge_iso.md document to the dev section in the top-level README and adjusted its intro to denote the dev audience.
Thanks!

/lgtm

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dhellmann, fzdarsky, ggiguash

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[openshift-ci]

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