HaikuDepot: Languages List

Abstacts the list of supported languages into
the LanguageModel class preventing use of
List. Also; fix a few cases where newer
logging techniques may have caused incorrect
logic flow.

Relates To #15534

Change-Id: I144fe4788abdaf0d93e53eeabc97b3f7aa2ec710
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3085
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

HaikuDepot: Better Logging

Changes the logging in HD to use a macro for the
various log levels to declutter the code and to
make it easier to more systematically log.

Change-Id: I025970707a0a11e7e3aaa4b52fc91288af0183f5
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3018
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

HaikuDepot: Display User's Usage Conditions

A HaikuDepotServer may have previously agreed to
user usage conditions. If this is the case then
they are now able to view those conditions. There
were some problems with date formatting in this
change and so the date formatting logic has moved
into the HaikuDepot source code temporarily until
issues with the BDateTime class can be resolved;
most likely as a separate piece of work.

Relates to 15209

Change-Id: Ic3e5413d9139f410d7f7e8b566d4c56352dd2778
Reviewed-on: https://review.haiku-os.org/c/haiku/+/1870
Reviewed-by: Stephan Aßmus <superstippi@gmx.de>

HaikuDepot: Display User Usage Conditions

This change will allow the user to view the user
usage conditions from the HDS system in a
HaikuDepot window. The display of the text is not
currently well formatted in that the Markdown is
not yet properly parsed, but the display of the
data is working.

Relates to 15209

Change-Id: Ia6ad4ef995f5fe3c29c40221964e44d4554a033d
Reviewed-on: https://review.haiku-os.org/c/haiku/+/1750
Reviewed-by: waddlesplash <waddlesplash@gmail.com>