Migrate the bootstrap.js endpoint to Kibana Platform

[eliperelman]

Currently the logic for rendering the bootstrap.js endpoint exists in the legacy ui_render_mixin. Now that the server rendering service exists, we should be able to move this routing logic to the new platform.

[elasticmachine]

Pinging @elastic/kibana-platform (Team:Platform)

[pgayvallet]

I think we are going to have an issue here because the '/bundles/app/{id}/bootstrap.js' route uses try HAPI authent mode which we do not support on NP (and that we are currently not planing to support, see #41959)

kibana/src/legacy/ui/ui_render/ui_render_mixin.js

Lines 92 to 98 in 054ec70

	server.route({
	path: '/bundles/app/{id}/bootstrap.js',
	method: 'GET',
	config: {
	tags: ['api'],
	auth: authEnabled ? { mode: 'try' } : false,
	},

Other things to solve:

kibana/src/legacy/ui/ui_render/ui_render_mixin.js

Line 101 in 054ec70

const app = server.getUiAppById(id) || server.getHiddenUiAppById(id);

and (I think ?)

kibana/src/legacy/ui/ui_render/ui_render_mixin.js

Line 129 in 054ec70

...kbnServer.uiExports.styleSheetPaths

[joshdover]

It looks like we're only using the try auth mode to guard getting the theme:darkMode uiSetting. I really don't think there's a security risk to using the Kibana internal user for getting this setting instead.

The getUiApp + getHiddenUiApp logic is obsolete in the new platform because we always render the same core bundle.

I believe the uiExports.stylesheet issue will be resolved once sass-loader is added to our Webpack config in #53532 and all plugins migrate to using webpack imports for styles.

[pgayvallet]

The getUiApp + getHiddenUiApp logic is obsolete in the new platform because we always render the same core bundle.

Yes, however if we migrate now we will still need it to render legacy apps.

[tylersmalley]

Instead of migrating bootstrap.js, could we get rid of it and move the logic to the main page template? I have always felt that the bootstrap file was a needless delay.

[pgayvallet]

could we get rid of it and move the logic to the main page template? I have always felt that the bootstrap file was a needless delay.

We probably can yea, even if I'd prefer to first migrate the endpoint before trying to factorize it with the rendering service logic.

[pgayvallet]

could we get rid of it and move the logic to the main page template? I have always felt that the bootstrap file was a needless delay.

TIL, because of our CSP policy, we can't inline bootstrap.js into our main app template easily, so using a real js file can't be avoided, unless some quite impacting changes in our csp returning logic to allow to add an nonce-XXX to inline the script.