### The Problem

Using native Qt translation files (TS, `*.ts`) for exchanging with Transifex platform limits means to provide context
to translators to the only category:

| C++ source code                               | TS XML element                                 | Transifex metadata
|-----------------------------------------------|------------------------------------------------|:------------------:
| Class Name                                    | `<name>`ClassName`</name>`                     | Context
| `disambiguation` parameter of `tr()` function | `<comment>`Short comment`</comment>`           | N/A
| [Translator Comments](https://doc.qt.io/qt-5/i18n-source-translation.html#translator-comments) `//: ...` | `<extracomment>`Nice comment.`</extracomment>` | N/A

More details:
- https://docs.transifex.com/formats/introduction
- https://docs.transifex.com/formats/qt-ts
- https://doc.qt.io/qt-5/linguist-ts-file-format.html

### The Solution

[XLIFF](https://en.wikipedia.org/wiki/XLIFF) file format is supported by Transifex much better.

And Qt provides us with a stand-alone conversion tool `lconvert`.

```sh
$ lconvert -o bitcoin_es.xlf -i bitcoin_en.ts
```

Now more context options are available:

| TS XML element                                 | XLIFF XML element                               | Transifex metadata
|------------------------------------------------|-------------------------------------------------|:------------------:
| `<name>`ClassName`</name>`                     | `<group resname="ClassName">`...`</group>`      | yes
| `<comment>`Short comment`</comment>`           | `<context>`Short comment`</context>`            | yes
| `<extracomment>`Nice comment.`</extracomment>` | `<note from="developer">`Nice comment.`</note>` | yes

More details:
- https://docs.transifex.com/formats/xliff
- https://code.qt.io/cgit/qt/qttools.git/tree/src/linguist/lconvert/lconvert.pro?h=5.12.10

---

Looking for Concept (N)ACKs.
QT_TRANSLATE_NOOP("bitcoin-core", ""
"Fee estimation failed. Fallbackfee is disabled. Wait a few blocks or enable -"
"fallbackfee."),
QT_TRANSLATE_NOOP("bitcoin-core", ""
"Invalid amount for -maxtxfee=<amount>: '%s' (must be at least the minrelay "
"fee of %s to prevent stuck transactions)"),
QT_TRANSLATE_NOOP("bitcoin-core", ""
"More than one onion bind address is provided. Using %s for the automatically "
"created Tor onion service."),
QT_TRANSLATE_NOOP("bitcoin-core", ""
"Please check that your computer's date and time are correct! If your clock "
"is wrong, %s will not work properly."),
QT_TRANSLATE_NOOP("bitcoin-core", ""
"Please contribute if you find %s useful. Visit %s for further information "
"about the software."),
QT_TRANSLATE_NOOP("bitcoin-core", ""
"Prune configured below the minimum of %d MiB.  Please use a higher number."),
QT_TRANSLATE_NOOP("bitcoin-core", ""
"Prune: last wallet synchronisation goes beyond pruned data. You need to -"
"reindex (download the whole blockchain again in case of pruned node)"),
QT_TRANSLATE_NOOP("bitcoin-core", ""
"SQLiteDatabase: Failed to prepare the statement to fetch sqlite wallet "
"schema version: %s"),
QT_TRANSLATE_NOOP("bitcoin-core", ""
"SQLiteDatabase: Failed to prepare the statement to fetch the application id: "
"%s"),
QT_TRANSLATE_NOOP("bitcoin-core", ""
"SQLiteDatabase: Unknown sqlite wallet schema version %d. Only version %d is "
"supported"),
QT_TRANSLATE_NOOP("bitcoin-core", ""