[pournasserian]

Closes #2630
Closes #2633

What

Follow-ups from the independent reviews of #2613 and #2619 (F-FRM, #2426). The generated form now keeps the version it was made from and the values the person didn't touch.

• Base version. The hidden BaseVersion comes from the form being shown. A form refused for its own problems keeps the version it started from, so its next save is refused as a conflict instead of overwriting a change saved meanwhile.
• Untouched values.
  • FieldValues.Read and FactValues.Read take the stored value.
  • A posted text that shows the same as the stored value keeps the stored JSON. Seconds, offsets, 4.50 and LF line breaks survive a save.
  • Textarea line breaks are compared as LF. Only CR and CRLF are converted; other line separators stay as typed.
  • A stored value the field's current type no longer takes, as after a number field became text, is read from what was posted.
  • A text value with line breaks is shown in a textarea, since a single-line input drops them.
  • A textarea value that starts with a line break gets one more, since HTML drops the first.
• Which draft the form shows.
  • When the latest version isn't the published one and no set is reviewing it, a note names the version shown. It offers ?from=published. The update is still made from the latest version, so the version check holds.
  • A reverted create, which leaves nothing published, says so too.
• Entity facts.
  • The owner list holds every user, and disabled users are labelled "(disabled)", so a stored owner stays selected.
  • Owner ids are compared as GUIDs, and the stored text is kept.
  • A posted owner that is neither a user nor the fact's stored owner is refused.
• Untouched facts are kept exactly. A fact whose value and parts all show as stored is saved as stored, with its property order, spaces and any other properties.
• A stored plain value of a type made an entity type later shows as the value of a fact with no details yet, flagged unsourced. It no longer fails the save or is dropped. A fact is an object with a value, so a plain JSON object is a plain value too.
• An owner who is no user, such as one an agent set, shows as "Unknown user" on its own field and stays selected.
• The published version the values came from is posted under ?from=published, and whenever the latest version is the published one.
  • EntryEdit.PublishedBase carries it to EntryEdits. That checks it before the unit of work, and again against the version the operation is based on.
  • If publishing or a revert has moved on, the save is refused as a conflict, so it can't undo what was published.
• Booleans. An unchecked box saves false only when a value was stored, the field is required, or its fact details were given. Otherwise the field is left out, as an empty field is. A name-only edit no longer adds an unsourced {"value": false} fact.
• Fact details for an empty value are reported next to the field instead of being dropped.
• EntryEdits checks the rationale and sources before it writes.
• PickerField names aria-controls only while its list exists. The new axe check found it pointing at a missing id (Add search-backed pickers for reference and media fields #2622).

Why

• Keep the stored JSON when the text matches. No widget can show every stored value exactly, such as a date-time's seconds or a number's trailing zero. Comparing what the widget would show tells an untouched field from an edited one without client script.
• The base version stays the latest version under ?from=published. Another base would weaken the version check. The person sees which values they start from, and the set's diff shows the full change.

Tests

• Unit:
  • FieldValues.Read keeps stored date-times, numbers, CRLF text and JSON whose text matches, and replaces a changed one.
  • Unchecked booleans.
  • FactValues.Read keeps a stored owner's case and a stored time's seconds.
  • An unknown owner is refused.
  • HasDetails.
  • A JSON object without a value is a plain value.
  • A U+2028 in an edited text is kept.
  • A picker without matches has no aria-controls.
• Integration (EntryFormScreenTests, EntityFormScreenTests):
  • The Keep the entry form's base version, stop rewriting untouched values, and say which draft the form shows #2630 overwrite scenario ends in the conflict message.
  • After a published revert, the form names the reverted draft and offers the published version. A form from a published version since replaced is refused.
  • A reverted create says so.
  • Editing an entry written before its type held facts shows its plain values, a JSON object included, and saves its facts.
  • A title-only edit keeps several values exactly as stored:
    • a CRLF body that starts with a line break;
    • a multi-line text value, which gets a textarea;
    • the date-time text 09:30:45.5+02:00;
    • 4.50;
    • an absent boolean.
  • EntryEdits refuses a blank source, and an update whose published base isn't the published version. Neither writes a version or an event.
  • A form open on the published version when a revert publishes an older one is refused on save.
  • An untouched value after its field changed from number to text is saved as text.
  • Editing a published entry proposes an update from version 1, and a stray draft is named. The saved set is submitted from the set view.
  • The unknown enum value is reported.
  • A name-only entity edit keeps the other fact byte for byte, including a disabled upper-case owner, a source in another order with a trailing space, and times with seconds and offsets. It also keeps an owner who is no user, and an absent boolean.
  • Problems and the unsourced marker sit inside their field's fact fieldset.
  • A forged owner and fact details without a value are refused.
• Browser:
  • A title-only edit in Chromium keeps a multi-line text and a rich text that starts with a line break.
  • The axe check covers a form with every widget, and a refused submit. The keyboard path through a form and its save is FormPickerTests from Add search-backed pickers for reference and media fields #2622.

dotnet build -warnaserror, the unit and bUnit suite, the browser tests and the integration suite pass locally. No new package and no new project reference.

Checklist

• Linked to an issue a maintainer has confirmed
• Targets v2
• Tests or docs updated where behaviour changed
• No tool-generated co-author trailers or footers