Correct external DB instructions for foreman-{deb,el}

[ekohl]

When Katello isn't present, you don't need the Candlepin and Pulp databases. With this change, the scenario becomes correct and can be shown.

This is now a draft since I'm not entirely sure if it's all correct. I'm going to rely on the preview to tell me that.

• [x] I am familiar with the contributing guidelines.

Please cherry-pick my commits into:

• [x] Foreman 3.7/Katello 4.9 (planned Satellite 6.14)
• [x] Foreman 3.6/Katello 4.8
• [ ] Foreman 3.5/Katello 4.7 (Satellite 6.13)
• [ ] Foreman 3.4/Katello 4.6 (EL8 only)
• [ ] Foreman 3.3/Katello 4.5 on EL7 & EL8 (Satellite 6.12 on EL8 only; orcharhino 6.4/6.5 on EL8 only)
• [ ] Foreman 3.2/Katello 4.4 on EL7 & EL8
• [ ] Foreman 3.1/Katello 4.3 on EL7 & EL8 (Satellite 6.11 EL7/8; orcharhino 6.3 on EL7/8)
• We do not accept PRs for Foreman older than 3.1.

[github-actions[bot]]

The PR preview for a38cbf83d4082eca17e134f32273a942f7699003 is available at theforeman-foreman-documentation-preview-pr-2396.surge.sh

The following output files are affected by this PR:

• Administering_Project/index-foreman-deb.html
• Administering_Project/index-foreman-el.html
• Administering_Project/index-katello.html
• Administering_Project/index-orcharhino.html
• Administering_Project/index-satellite.html
• Installing_Server/index-foreman-deb.html
• Installing_Server/index-foreman-el.html
• Installing_Server/index-katello.html
• Installing_Server/index-orcharhino.html
• Installing_Server/index-satellite.html
• Installing_Server_Disconnected/index-satellite.html
• Upgrading_Project/index-foreman-el.html

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show diff as HTML

[ekohl]

I noticed that the PostgreSQL path we use is for Debian 11, which uses PostgreSQL 13. Ubuntu 20.04 uses PostgreSQL 12, so the path is different.

This may need a bit more work.

[ekohl]

I've taken a bit of time to split the commits into more logical changes. Each individual commit should be reasonably easy to review.

[ekohl]

I had some difficulty with the size of this PR and I've opened https://github.com/theforeman/foreman-documentation/pull/2514 with some the things that I are ready to be merged.

[ekohl]

Turns out the snippet isn't exactly the same: one has xref, the other doesn't.

[ekohl]

I decided to split this up in smaller pieces so we can at least merge those: https://github.com/theforeman/foreman-documentation/pull/3172 https://github.com/theforeman/foreman-documentation/pull/3173

[ekohl]

Will rebase once https://github.com/theforeman/foreman-documentation/pull/3167 is merged.

[maximiliankolb]

FYI: I have cherry-picked 24017acd47917de530d3f67c652f6efd29092e9d and f4ff4b3318af7fd94f41b0be13c1d8be75d784fe in PR https://github.com/theforeman/foreman-documentation/pull/3264