reason: the handsets use this frequency band only.

reason: N870 does not restrict the provd version to >= 0.2 like the N720, so
we need to make it compatible with previous versions.

reason: if the extension is shorter than 4 characters, we want a 4 character code anyway.

reason: v2.17.2 supports fixed handset numbering.

WAZO-2313: fix Yealink v82 firmwares

Reviewed-by: https://github.com/apps/wazo-production-sf

Why: not available anymore

add template option for Aastra/Mitel 68xx

Reviewed-by: https://github.com/apps/wazo-production-sf

WP-344: add Greandstream HT80x ATAs

Reviewed-by: https://github.com/apps/wazo-production-sf

WP-343: add Grandstream GRP261x series

Reviewed-by: https://github.com/apps/wazo-production-sf

Why: easier to manage function keys

WP-342: add Grandstream GXV33xx

Reviewed-by: https://github.com/apps/wazo-production-sf

Why: the server does not know the certificates