Expand the designated signers to user ID, email, and domain queries.

- This allows one to require a signature from sequoia-pgp.org, for
    example.

  - See #248.

src/cli/decrypt.rs

@@ -109,7 +109,7 @@ pub struct Command {
     pub signatures: Option<usize>,
 
     #[command(flatten)]
-    pub signers: CertDesignators<CertFileArgs,
+    pub signers: CertDesignators<FileCertUserIDEmailDomainArgs,
                                  SignerPrefix,
                                  OptionalValue,
                                  ToVerifyDoc>,

src/cli/download.rs

@@ -70,7 +70,7 @@ inline.
     pub signature: Option<String>,
 
     #[command(flatten)]
-    pub signers: CertDesignators<CertFileArgs,
+    pub signers: CertDesignators<FileCertUserIDEmailDomainArgs,
                                  SignerPrefix,
                                  OptionalValue,
                                  ToVerifyDoc>,

src/cli/verify.rs

@@ -126,7 +126,7 @@ pub struct Command {
     pub signatures: usize,
 
     #[command(flatten)]
-    pub signers: CertDesignators<CertFileArgs,
+    pub signers: CertDesignators<FileCertUserIDEmailDomainArgs,
                                  SignerPrefix,
                                  OptionalValue,
                                  ToVerifyDoc>,