[Fleet] Add Edit ReadMe Functionality To Custom Integrations

[Supplementing]

Closes #212957

Adds editing of the automatically-generated readMe file on custom integrations.

• Allows the user to make edits and then save the readMe changes via a new endpoint
• Reloads the UI after making changes to reflect the updated readMe
• Automatically updates associated policies

To test the new endpoint, you will need a custom integration installed, then use it as such

PUT kbn:/api/fleet/epm/custom_integrations/{pkgName}
{
    "readMeData": "New README content here"

}

Screen.Recording.2025-04-16.at.12.35.32.PM.mov

Acceptance criteria

• An "edit" button with an icon appears in the README section of the integration overview page for custom integrations generated by automatic import
• Clicking the "edit" button should open a modal (TBD) containing a markdown editor that allows the user to edit the content
• Users can save their changes, and the updated README content is persisted
• Saving updates the version of the package and reloads the content
• Saving also starts updating policies automatically

Checklist

Check the PR satisfies following conditions.

Reviewers should verify this PR satisfies this list as well.

• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support
• Documentation was added for features that require explanation or tutorials
• Unit or functional tests were updated or added to match the most common scenarios
• If a plugin configuration key changed, check if it needs to be allowlisted in the cloud and added to the docker list
• This was checked for breaking HTTP API changes, and any breaking changes have been approved by the breaking-change committee. The release_note:breaking label should be applied in these situations.
• Flaky Test Runner was used on any tests changed
• The PR description includes the appropriate Release Notes section, and the correct release_note:* label is applied per the guidelines

Identify risks

N/A

Release Note

Adds edit functionality to custom integrations, allowing a user to edit the README file of a custom integration and save it to be persisted. Additionally, saving will automatically increment the version of the integration and update all associated policies.

[Supplementing]

/CI

[elasticmachine]

Pinging @elastic/fleet (Team:Fleet)

[Supplementing]

@elasticmachine merge upstream

[Supplementing]

@elasticmachine merge upstream

[nchaulet]

Should we add a changelog item if there is none present?
I tried to update the readme of a custom integration without one, created with

POST kbn:/api/fleet/epm/custom_integrations
{
 "integrationName": "test",
 "datasets": []
}

and got the following error

[nchaulet]

Actually looks like the error was related to that change #217257 I will comment there

[nchaulet]

LGTM 🚀

[Supplementing]

@elasticmachine merge upstream

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: b8a0f11

Metrics [docs]

Module Count

Fewer modules leads to a faster build time

id	before	after	diff
fleet	1186	1189	+3

Public APIs missing comments

Total count of every public API that lacks a comment. Target amount is 0. Run node scripts/build_api_docs --plugin [yourplugin] --stats comments for more detailed information.

id	before	after	diff
fleet	1406	1410	+4

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
fleet	1.7MB	1.7MB	+3.8KB

Page load bundle

Size of the bundles that are downloaded on every page load. Target size is below 100kb

id	before	after	diff
fleet	164.2KB	164.5KB	+367.0B

Unknown metric groups

API count

id	before	after	diff
fleet	1535	1539	+4

History

• 💚 Build #295122 succeeded b06731d
• 💔 Build #295107 failed 27114fd
• 💛 Build #294339 was flaky 4f1d684
• 💔 Build #294301 failed d42d437
• 💔 Build #293956 failed 82354c7