Support pulling mod by manifest hash

[thespad]

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• I have read the contributing guideline and understand that I have made the correct modifications

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Description:

Closes #922

Further work needed to support a wider range of formats for the mods as currently it only works with the mods:tag@sha256:hash format and not mods@sha256:hash format.

Benefits of this PR and context:

Given the following inputs for DOCKER_MODS:

linuxserver/mods:universal-tshoot@sha256:d31f2d4a88a0c5d98f6bf7f4725e228959b6d22dcd14d44c7a755521f007cd98
linuxserver/mods@sha256:d31f2d4a88a0c5d98f6bf7f4725e228959b6d22dcd14d44c7a755521f007cd98
linuxserver/mods:universal-tshoot

The data is parsed as:

$ENDPOINT         $USERNAME     $REPO   $FULLTAG                                                                                  $TAG              $TAGSHA
linuxserver/mods  linuxserver   mods    universal-tshoot@sha256:d31f2d4a88a0c5d98f6bf7f4725e228959b6d22dcd14d44c7a755521f007cd98  universal-tshoot  sha256:d31f2d4a88a0c5d98f6bf7f4725e228959b6d22dcd14d44c7a755521f007cd98
linuxserver/mods  linuxserver   mods                                                                                                                sha256:d31f2d4a88a0c5d98f6bf7f4725e228959b6d22dcd14d44c7a755521f007cd98
linuxserver/mods  linuxserver   mods                                                                                              universal-tshoot

And then correctly fetched from the remote registry and saved as:

linuxserver.mods.universal-tshoot.d31f2d4a88a0c5d98f6bf7f4725e228959b6d22dcd14d44c7a755521f007cd98.tar.xz
linuxserver.mods.d31f2d4a88a0c5d98f6bf7f4725e228959b6d22dcd14d44c7a755521f007cd98.tar.xz
linuxserver.mods.universal-tshoot.tar.xz

How Has This Been Tested?

Source / References:

Note that technically when supplying a SHA hash the tag is not used by the docker CLI, thus all of the following will result in the same image being fetched:

linuxserver/mods:universal-tshoot@sha256:d31f2d4a88a0c5d98f6bf7f4725e228959b6d22dcd14d44c7a755521f007cd98
linuxserver/mods@sha256:d31f2d4a88a0c5d98f6bf7f4725e228959b6d22dcd14d44c7a755521f007cd98
linuxserver/mods:foo@sha256:d31f2d4a88a0c5d98f6bf7f4725e228959b6d22dcd14d44c7a755521f007cd98

But from a mod perspective they're treated as 3 different mods because of how we store the data about them (Layer SHA, not manifest SHA).

[quietsy]

Haven't tested but looks good