Third-party modules cannot control translation status

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See the MR

Looks good

Credits

Nice. Thank you!

I've merged this but I had a 2nd thought and, I think, this needs more architectural analysis

Now, I'm not sure anymore that we should offer per-instance status granularity. That would introduce some problems:

• If user makes no opinion (
  

  bs.status === NULL)</code > what is the status of a source when its instances have different statuses? You could argue that if at least one is TRUE, then it's TRUE. But wouldn't that be a too complex solution?</li>
    <li>I think there should be no per-instance status, but only <em>per-plugin status</em> to get the things simpler:<ul>
    <li>Plugins might set the per-status in the plugin definition (attribute).</li>
    <li>The <code>bs.status

  column defaults to 0

• When a new source is added, if the hash exists AND is 1 we do nothing (1 always wins over 0). Otherwise we set bs.status to the plugin definition status.
• Third-party are able to implement hook_babel_translation_type_info() to change the plugin-based initial status.

Reverted to clarify more the solution

Move status from StringTranslation into Source

The new solution does not fully work; I am able to configure it per plugin, but it is difficult to implement feature 3539510.