Support querystring and anchor for local links in Delivery API output

[kjac]

Prerequisites

• I have added steps to test this contribution in the description below

If there's an existing issue for this PR then this fixes #18475

Description

See the linked issue for a description. This PR fixes the issue.

As it turns out, this:

• Applies to both link querystrings and anchors
• Only applies to internal (local) links

Property naming

Although this fix applies to both querystrings and anchors, I have opted to call the new property QueryString to align with the ApiLink used by the multi URL picker to generate output for the Delivery API. For ApiLink, the QueryString property can also contain anchors.

Testing this PR

Make sure that both querystrings and anchor links are included for:

• Internal (local) links
• External links

Remember to test with:

• Default RTE output
• RTE output as JSON

[bjarnef]

@kjac an option may also be to split the hash into a Fragment property https://learn.microsoft.com/en-us/dotnet/api/system.uri.fragment?view=net-9.0

But currently both exist in the Querystring field in link picker, which is fine as long fragment is the last part (but I don't think there are specific validation for this at the moment).

[AndyButland]

Looks good from my perspective, apart from a small issue that needs resolving to avoid a binary breaking change (noted inline). Fine for me to merge once that is resolved, and when you have considered @bjarnef's feedback too.

Have tested with various links, with expected results:

As Markup:

<p>Test <a href=\"/test-landing/#test\" title=\"Test Landing\" data-anchor=\"#test\" data-start-item-path=\"home\" data-start-item-id=\"ac2038d9-dfc2-4294-b778-7edf90d1a178\">link</a>.</p>\n
<p>Test <a href=\"/?foo=bar\" title=\"Home\" data-anchor=\"?foo=bar\" data-start-item-path=\"home\" data-start-item-id=\"ac2038d9-dfc2-4294-b778-7edf90d1a178\">link 2</a>.</p>\n
<p>Test <a href=\"https://umbraco.com?foo=bar\" data-anchor=\"?foo=bar\">link 3</a>.</p>

As JSON:

"elements": [
    {
        "text": "Test ",
        "tag": "#text"
    },
    {
        "tag": "a",
        "attributes": {
            "anchor": "#test",
            "title": "Test Landing",
            "route": {
                "path": "/test-landing/",
                "queryString": "#test",
                "startItem": {
                    "id": "ac2038d9-dfc2-4294-b778-7edf90d1a178",
                    "path": "home"
                }
            }
        },
        "elements": [
            {
                "text": "link",
                "tag": "#text"
            }
        ]
    },
    {
        "text": ".",
        "tag": "#text"
    }
]
},
{
"tag": "p",
"attributes": {},
"elements": [
    {
        "text": "Test ",
        "tag": "#text"
    },
    {
        "tag": "a",
        "attributes": {
            "anchor": "?foo=bar",
            "title": "Home",
            "route": {
                "path": "/",
                "queryString": "?foo=bar",
                "startItem": {
                    "id": "ac2038d9-dfc2-4294-b778-7edf90d1a178",
                    "path": "home"
                }
            }
        },
        "elements": [
            {
                "text": "link 2",
                "tag": "#text"
            }
        ]
    },
    {
        "text": ".",
        "tag": "#text"
    }
]
},
{
"tag": "p",
"attributes": {},
"elements": [
    {
        "text": "Test ",
        "tag": "#text"
    },
    {
        "tag": "a",
        "attributes": {
            "href": "https://umbraco.com?foo=bar",
            "anchor": "?foo=bar"
        },
        "elements": [
            {
                "text": "link 3",
                "tag": "#text"
            }
        ]
    },
    {
        "text": ".",
        "tag": "#text"
    }
]
}
],

[kjac]

The link picker does indeed combine hash and querystring into the same field:

...and since ApiLink potentially also has both hash and querystring in the same field, I figure it makes sense to continue this logic.

[bjarnef]

Yes, technically hash isn't part of Uri class though IIRC.
Perhaps something to consider later. It can possible simplify frontend when having a mix of different types of link, but in our use-case we just parse the link in frontend meaning an arrow down icon when down to anchor on same page, otherwise an arrow right icon.