This updates all source files to use a new standard header for copyright
and license declaration. Notably, copyright no longer includes a date,
and we now use the standard SPDX-License-Identifier header.
This commit was done almost entirely mechanically with perl, and then
some minimal manual fixes.
Updates #6865
Signed-off-by: Will Norris <will@tailscale.com>
The `tailscale web` UI is the primary interface for Synology and Home
Assistant users (and perhaps others), so is the logical place to put our
open source license notices. I don't love adding things to what is
currently a very minimal UI, but I'm not sure of a better option.
Updates tailscale/corp#5780
Signed-off-by: Will Norris <will@tailscale.com>