NIFI-9776 Adding the possibility to export flow definition with referenced services

[simonbence]

This PR aims to open the possibility to export Flow Definition of a group with the referenced Controller Servcies from outside the scope of the Process Group.

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Enables X functionality; fixes bug NIFI-YYYY.

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[simonbence]

Hi @bbende ! Can you please take a look if you have some time? I think, as this change is connected to the registry, your input would be most useful. Many thanks!

[bbende]

Backend code looks good, and functionality is working as expected, nice work!

My only comment is around the wording of the menu items. Personally I know what the two options mean, but I wonder if the word "referenced" on its own is clear enough.

Take an example like this, process group being downloaded has:

• Processor A referencing service A, where service A is inside the group
• Processor A referencing service B, where service B is in a parent group

To me, these are both "referenced" services, its just that one is inside the PG and one is outside. So if you choose "without referenced services" we aren't saying we'll exclude both referenced services, we are just excluding the references that come from outside.

I'm not sure if added the word "external" or something else could make it a little clearer for users that aren't familiar with this.

[andrewmlim]

My initial impression of the UI is the same as Bryan's: "referenced" services could be downloaded with both options. It's more a matter of whether the services are in or out of the scope of the process group.

Suggested alternative:

• Without externally referenced services
• With externally referenced services

or if those are too long:

• Without external services
• With external services

[andrewmlim]

For the User Guide update, I understand the thinking behind adding two main bullets. But to reduce repetition, I thought we could add something like this:

- *Download flow definition*: This option allows the user to download the flow definition of the process group as a JSON file. The file can be used as a backup or imported into a link:https://nifi.apache.org/registry.html[NiFi Registry^] using the <<toolkit-guide.adoc#nifi_CLI,NiFi CLI>>. There are two choices when downloading a flow definition:

** *Without external services*: Controller services referenced by the selected process group but outside its scope (e.g., services in a parent group) _will not be_ included in the flow definition.
** *With external services*: Controller services referenced by the selected process group but outside its scope (e.g., services in a parent group) _will be_ included in the flow definition.

(Note: If "Download flow definition" is selected for a versioned process group, there is no versioning information in the download. In other words, the resulting contents of the JSON file is the same whether the process group is versioned or not.)

[andrewmlim]

@simonbence I think it would be more helpful if this Note is included with the "Download flow definition" section. It could get lost here at the end.

[simonbence]

I tried it that way as well and the rendered documentation looked pretty bad: the node did cut the list into two separate parts.

[andrewmlim]

@simonbence OK, no problem. LGTM +1 then.