ITSamMed

It seems like this may be related specifically to Elliptic Curve Digital Signature Algorithm (ECDSA). This builds just fine: `Clients.builder().setPrivateKey(Jwts.SIG.RS256.keyPair().build().private).build()` This fails to build: `Clients.builder().setPrivateKey(Jwts.SIG.ES256.keyPair().build().private).build()`

What's weird is that passing an unencrypted PEM file path whose private key is ES512 also seems to work... `openssl genpkey -out unencrypted.key -algorithm EC -pkeyopt ec_paramgen_curve:P-521` `Clients.builder().setPrivateKey("unencrypted.key").build()`