Clarified defined logic, param checking, and strings

This commit clarifies the defined logic within the codebase to use
defined where needed, and remove where not correct.  Additionally
added more specific param checking on methods to ensure we're not
validating params we're not expecting.  Also updated to single
quotes where interpolation isn't required.

lib/Pasteburn/Config.pm

@@ -110,7 +110,7 @@ C<Pasteburn::Config> loads the project config.
 
 Load the config and return a C<Pasteburn::Config> object.
 
-Required keys and values are validated during load, and exception thrown if not defined or containing the default values.
+Required keys and values are validated during load, and exception thrown if key does not exist and doesn't match the expected values.
 
 =back
 

lib/Pasteburn/Crypt/Hash.pm

@@ -63,7 +63,7 @@ sub validate {
         @_,
     };
 
-    if ( !$arg->{hash} ) {
+    if ( !defined $arg->{hash} ) {
         die "hash is required\n";
     }
 

lib/Pasteburn/Crypt/Storage.pm

@@ -30,7 +30,7 @@ sub encode {
         @_,
     };
 
-    if ( !$arg->{secret} ) {
+    if ( !defined $arg->{secret} ) {
         die "secret argument is required\n";
     }
 
@@ -44,7 +44,7 @@ sub decode {
         @_,
     };
 
-    if ( !$arg->{secret} ) {
+    if ( !defined $arg->{secret} ) {
         die "secret argument is required\n";
     }
 

lib/Pasteburn/Model/Secrets.pm

@@ -89,7 +89,7 @@ sub get {
     my ( @where, @bind_values );
 
     foreach my $key ( keys %{$arg} ) {
-        if ( !defined $arg->{$key} ) {
+        if ( !$arg->{$key} ) {
             next;
         }
 
@@ -117,7 +117,7 @@ sub store {
         @_,
     };
 
-    foreach my $attribute ( 'passphrase', 'secret' ) {
+    foreach my $attribute (qw{passphrase secret}) {
         if ( !defined $self->{$attribute} ) {
             die "$attribute is required";
         }
@@ -208,11 +208,11 @@ sub validate_passphrase {
     };
 
     if ( !Scalar::Util::blessed($self) ) {
-        die "validate_passphrase must be called as an object method";
+        die 'validate_passphrase must be called as an object method';
     }
 
     if ( !$self->id ) {
-        die "validate_passphrase cannot be run for a nonexistent secret";
+        die 'validate_passphrase cannot be run for a nonexistent secret';
     }
 
     if ( !defined $arg->{passphrase} ) {
@@ -225,7 +225,7 @@ sub validate_passphrase {
     # but not allow an undef to be stored.
     # although unlikely to fail, still verify the hashed passphrase is in the object.
     if ( !defined $self->passphrase ) {
-        die "passphrase is not set";
+        die 'passphrase is not set';
     }
 
     my $crypt = Pasteburn::Crypt::Hash->new();
@@ -241,15 +241,15 @@ sub decode_secret {
     };
 
     if ( !Scalar::Util::blessed($self) ) {
-        die "decode_secret must be called as an object method";
+        die 'decode_secret must be called as an object method';
     }
 
     if ( !$self->id ) {
-        die "decode_secret cannot be run for a nonexistent secret";
+        die 'decode_secret cannot be run for a nonexistent secret';
     }
 
     if ( !defined $arg->{passphrase} ) {
-        die "passphrase is required";
+        die 'passphrase is required';
     }
 
     my $crypt_storage  = Pasteburn::Crypt::Storage->new( passphrase => $arg->{passphrase} );
@@ -268,11 +268,11 @@ sub delete_secret {
     my $self = shift;
 
     if ( !Scalar::Util::blessed($self) ) {
-        die "delete_secret must be called as an object method";
+        die 'delete_secret must be called as an object method';
     }
 
     if ( !$self->id ) {
-        die "delete_secret cannot be run for a nonexistent secret";
+        die 'delete_secret cannot be run for a nonexistent secret';
     }
 
     my $sql = q{

t/lib/Pasteburn/Test.pm

@@ -149,14 +149,14 @@ sub create_test_app {
         @_,
     );
 
-    foreach my $required ( keys %args ) {
+    foreach my $required ( qw{config} ) {
         if ( !defined $args{$required} ) {
             die "$required is required";
         }
     }
 
     if ( !ref $args{config} eq 'HASH' ) {
-        die "config must be a hashref";
+        die 'config must be a hashref';
     }
 
     override(