extra_js_urls and extra_css_urls should respect base_url setting

[simonw]

Originally posted by @simonw in #1033 (comment)

Refs #1023

[simonw]

@psychemedia said: #1033 (comment)

How does /-/static relate to current guidance docs around static regarding the --static option and metadata formulations such as "extra_js_urls": [ "/static/app.js"] (I've not managed to get this to work in a Jupyter server proxied set up; the datasette / jupyter server proxy repo may provide a useful test example, eg via MyBinder, for folk to crib from?)

[simonw]

I'll need to update these docs once there's a solution for this in place: https://docs.datasette.io/en/latest/custom_templates.html#serving-static-files

[simonw]

I think I'll do this by looking for URLs that start with / - since it's also possible to have full https://... URLs in that setting.

{
    "extra_css_urls": [
        "/static/styles.css"
    ],
    "extra_js_urls": [
        "/static/app.js"
    ]
}

I need to think about the extra_css_urls and extra_js_urls plugin hooks too: https://docs.datasette.io/en/stable/plugin_hooks.html#extra-css-urls-template-database-table-columns-view-name-request-datasette

[simonw]

Implemented in a4ca26a