asiidoctor errors while building documentation

[sandrobonazzola]

Description of the problem

Type of problem?

Documentation issue

asciidoctor report errors while building the documentation:

Generating... 
asciidoctor: ERROR: model.adoc: line 3123: invalid part, must have at least one section (e.g., chapter, appendix, etc.)
asciidoctor: WARNING: common/upgrade/proc-Replacing_SHA-1_Certificates_with_SHA-256_Certificates.adoc: line 72: no callout found for <1>
asciidoctor: WARNING: common/upgrade/proc-Replacing_SHA-1_Certificates_with_SHA-256_Certificates.adoc: line 179: no callout found for <1>
asciidoctor: WARNING: common/upgrade/proc-Replacing_SHA-1_Certificates_with_SHA-256_Certificates.adoc: line 72: no callout found for <1>
asciidoctor: WARNING: common/upgrade/proc-Replacing_SHA-1_Certificates_with_SHA-256_Certificates.adoc: line 179: no callout found for <1>
asciidoctor: WARNING: common/upgrade/proc-Replacing_SHA-1_Certificates_with_SHA-256_Certificates.adoc: line 72: no callout found for <1>
asciidoctor: WARNING: common/upgrade/proc-Replacing_SHA-1_Certificates_with_SHA-256_Certificates.adoc: line 179: no callout found for <1>
asciidoctor: ERROR: model.adoc: line 85: level 0 sections can only be used when doctype is book
asciidoctor: ERROR: model.adoc: line 469: level 0 sections can only be used when doctype is book
asciidoctor: ERROR: model.adoc: line 1188: level 0 sections can only be used when doctype is book
asciidoctor: ERROR: model.adoc: line 2225: level 0 sections can only be used when doctype is book
asciidoctor: ERROR: model.adoc: line 3123: level 0 sections can only be used when doctype is book
asciidoctor: ERROR: model.adoc: line 34254: level 0 sections can only be used when doctype is book
asciidoctor: ERROR: model.adoc: line 56401: level 0 sections can only be used when doctype is book
asciidoctor: ERROR: model.adoc: line 56549: level 0 sections can only be used when doctype is book
                    done in 3.684 seconds.

See https://github.com/oVirt/ovirt-site/actions/runs/3686330423/jobs/6238411859

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