sandbox
usage:
{{doi|10.1016/j.techfore.2009.07.009}}
generated link:
https://dx.doi.org/10.1016/j.techfore.2009.07.009
basic:
doi:[https://dx.doi.org/{{{doi|}}} {{{doi|}}}]
with nil value warning:
doi:[https://dx.doi.org/{{{doi|}}} {{{doi|{{orange|doi required}}}}}]
