Batch convert tEXt PNG badges to iTXt PNG badges

Badges metadata is written when the badge is issued. And never touched after that.

Old badges have metadata stored into tEXt field. New ones (see MDL-49103) into iTXt.

Badges using the old tEXt field are unable to be uploaded to backpacks and other Badge facilities because iTXt is what the compliant products (via spec) are expecting.

To have a tEXt to iTXt converter may be useful (step 1).

Then, once available and able to convert any PNG (replacing or adding the metadata, not sure at this moment...) we could apply it to various, complementary, solutions. I'd call this (step 2):

• Create a CLI able to convert any badge.
• Create a task able to go processing all the old badges.
• Create an UI, so every user is able, when managing their own badges in Moodle, to apply for the conversion.
• ....

That would enable automagically far better integration with other Badge-compliant tools (Badgr included, right now we cannot upload any old PNG because of this).

Just an idea, with 2 steps, ciao