We need to (and already did) define our own identifier for ciphers,
because the gnutls/nss identifiers must be abstracted.
Don't use a string for that. The number of supported ciphers
is not generic but fixed and known at compiler time. An enum
is better suited.
- avoid "const gsize" as type for function arguments.
- consistently use "guint8 *" type for binary data, instead
of "char *", which indicates a NUL terminated C string.
- drop nm_crypto_encrypt(). It's not actually used outside of
"nm-crypto.c".
- rename internal _nm_crypto_*() functions that are only used
in tests. It's so much nicer to visually recognize functions
that are used for testing only.
Rename _nm_crypto_verify_cert() to _nm_crypto_verify_x509().
Also, don't let it return a NMCryptoFileFormat result. This
function only checks for a particular format, hence it
should only return true/false.
Also, fix setting error output argument when the function fails.
Follow our convention, that items in headers are all named with
an "NM" prefix.
Also, "nm-crypto-impl.h" contains internal functions that are to be implemented
by the corresponding crypto backends. Distinguish their names as well.
There are two aspects: the public crypto API that is provided by
"nm-crypto.h" header, and the internal header which crypto backends
need to implement. Split them.
