add charset modifier to secret generation (#521)

since we need special chars in passwords for a recipe we are working on, i have added the option to specify a charset in the same way as the length can be setted.
i did not change anything in the behaviour, so if length is not specified, the charset gets ignored whether it is there or not.

you can specify the following:
`charset=default` - Results in passgen.AlphabetDefault being used
`charset=special` - Results in passgen.AlphabetSpecial being used
`charset=safespecial` - Results in `!@#%^&*_-+=` being used (so it is AlphabetSpecial without the dollar sign)
`charset=default,special` or `charset=special,default` - Results in passgen.AlphabetDefault + passgen.AlphabetSpecial being used
`charset=default,safespecial` or `charset=safespecial,default` - Results in passgen.AlphabetDefault + `!@#%^&*_-+=` being used ((so it is AlphabetSpecial without the dollar sign)

PR for the docs: toolshed/docs.coopcloud.tech#271

Co-authored-by: p4u1 <p4u1@noreply.git.coopcloud.tech>
Reviewed-on: toolshed/abra#521
Reviewed-by: p4u1 <p4u1@noreply.git.coopcloud.tech>
Co-authored-by: Apfelwurm <Alexander@volzit.de>
Co-committed-by: Apfelwurm <Alexander@volzit.de>

pkg/secret/secret_test.go

@@ -17,16 +17,37 @@ func TestReadSecretsConfig(t *testing.T) {
 	assert.Equal(t, "test_example_com_test_pass_one_v2", secretsFromConfig["test_pass_one"].RemoteName)
 	assert.Equal(t, "v2", secretsFromConfig["test_pass_one"].Version)
 	assert.Equal(t, 0, secretsFromConfig["test_pass_one"].Length)
+	assert.Equal(t, "abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ23456789", secretsFromConfig["test_pass_one"].Charset)
 
 	// Has a length modifier
 	assert.Equal(t, "test_example_com_test_pass_two_v1", secretsFromConfig["test_pass_two"].RemoteName)
 	assert.Equal(t, "v1", secretsFromConfig["test_pass_two"].Version)
 	assert.Equal(t, 10, secretsFromConfig["test_pass_two"].Length)
+	assert.Equal(t, "abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ23456789", secretsFromConfig["test_pass_two"].Charset)
 
 	// Secret name does not include the secret id
 	assert.Equal(t, "test_example_com_pass_three_v2", secretsFromConfig["test_pass_three"].RemoteName)
 	assert.Equal(t, "v2", secretsFromConfig["test_pass_three"].Version)
 	assert.Equal(t, 0, secretsFromConfig["test_pass_three"].Length)
+	assert.Equal(t, "abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ23456789", secretsFromConfig["test_pass_three"].Charset)
+
+	// Has a length modifier and a charset=default,safespecial modifier
+	assert.Equal(t, "test_example_com_test_pass_four_v1", secretsFromConfig["test_pass_four"].RemoteName)
+	assert.Equal(t, "v1", secretsFromConfig["test_pass_four"].Version)
+	assert.Equal(t, 12, secretsFromConfig["test_pass_four"].Length)
+	assert.Equal(t, "abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ23456789!@#%^&*_-+=", secretsFromConfig["test_pass_four"].Charset)
+
+	// Has a length modifier and a charset=default,special modifier
+	assert.Equal(t, "test_example_com_test_pass_five_v1", secretsFromConfig["test_pass_five"].RemoteName)
+	assert.Equal(t, "v1", secretsFromConfig["test_pass_five"].Version)
+	assert.Equal(t, 12, secretsFromConfig["test_pass_five"].Length)
+	assert.Equal(t, "abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ23456789!@#$%^&*_-+=", secretsFromConfig["test_pass_five"].Charset)
+
+	// Has only a charset=default,special modifier, which gets setted but ignored in the generation
+	assert.Equal(t, "test_example_com_test_pass_six_v1", secretsFromConfig["test_pass_six"].RemoteName)
+	assert.Equal(t, "v1", secretsFromConfig["test_pass_six"].Version)
+	assert.Equal(t, 0, secretsFromConfig["test_pass_six"].Length)
+	assert.Equal(t, "abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ23456789!@#$%^&*_-+=", secretsFromConfig["test_pass_six"].Charset)
 }
 
 func TestReadSecretsConfigWithLongDomain(t *testing.T) {