sha1 returns the lowercase hex string presenration of the SHA-1 hash of the
given input value.
(sha1 "")➜"da39a3ee5e6b4b0d3255bfef95601890afd80709"(sha1 "hello")➜"aaf4c61ddcc5e8a2dabede0f3b482cd9aea9434d"
datais an arbitrary expression.
sha1 evaluates the given expression and coalesces the result to a
string. If either of those steps fail, an error is returned. Otherwise the
function will calculate the SHA-1 hash and return the hex presentation (a string
of 40 characters).