remove c7 only content from bpmn and modeler docs

[christinaausley]

Description

Relates to and partially addresses https://github.com/camunda/documentation-team/issues/71.

This removes:

• Loop task marker event
• Any note that the escalation event is supported in Camunda 7, but not yet in Camunda 8.
• Defining templates in C7
• Disable history-time-to-live hint and default HTTL for C7 only. Same for the HTTL page.

A few open questions:

• Are condition events C7-only? If so, we should remove this.
• Are Camunda Forms C7-only? If so, should we remove this? It is a larger chunk of info, so would probably handle in a separate PR.

When should this change go live?

• This is a bug fix, security concern, or something that needs urgent release support. (add bug or support label)
• This is already available but undocumented and should be released within a week. (add available & undocumented label)
• This is on a specific schedule and the assignee will coordinate a release with the DevEx team. (create draft PR and/or add hold label)
• This is part of a scheduled alpha or minor. (add alpha or minor label)
• There is no urgency with this change (add low prio label)

PR Checklist

• My changes are for an upcoming minor release and:
  • are in the /docs directory (version 8.8).
  • are in the /versioned_docs/version-8.7/ directory (version 8.7).
• My changes are for an already released minor and are in a /versioned_docs directory.

• I added a DRI, team, or delegate as a reviewer for technical accuracy and grammar/style:
  • Engineering team review
  • Technical writer review via @camunda/tech-writers unless working with an embedded writer.

[barmac]

What is the replacement for the C7 customers? Why do we want to remove these docs?

[akeller]

What is the replacement for the C7 customers? Why do we want to remove these docs?

We want to be laser-focused on the C8 experience on docs.camunda.io.

[wollefitz]

Lgtm but I'll leave the final review to @barmac as the modeling guidance section is owned by the Desktop Modeler team.

[barmac]

What is the replacement for the C7 customers? Why do we want to remove these docs?

We want to be laser-focused on the C8 experience on docs.camunda.io.

I understand, but what is the story for a C7 customer after this is merged? Are you adding these docs pages to https://docs.camunda.org/?

I'd like to avoid a situation where we remove documentation, and the users are left on their own.