Don't reference unaligned packed field

This will be an error some day.

warning: reference to packed field is unaligned
   --> src/certs/sev/cert/mod.rs:176:47
    |
176 |             1 => PublicKey::try_from(unsafe { &value.v1.body.data.key }),
    |                                               ^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: `#[warn(unaligned_references)]` on by default
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #82523 <rust-lang/rust#82523>
    = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)

Also bump the minimum stable compiler. The addr_of! macro was introduced in
1.51.0.

Signed-off-by: Connor Kuehl <[email protected]>

.github/workflows/test.yml

@@ -21,7 +21,7 @@ jobs:
           - nightly
           - beta
           - stable
-          - 1.42.0
+          - 1.51.0
         profile:
           - name: debug
           - name: release

src/certs/sev/cert/mod.rs

@@ -173,7 +173,9 @@ impl TryFrom<&Certificate> for PublicKey<Usage> {
 
     fn try_from(value: &Certificate) -> Result<Self> {
         match value.version() {
-            1 => PublicKey::try_from(unsafe { &value.v1.body.data.key }),
+            1 => PublicKey::try_from(unsafe {
+                &std::ptr::addr_of!(value.v1.body.data.key).read_unaligned()
+            }),
             _ => Err(ErrorKind::InvalidInput.into()),
         }
     }