Note: the attribute values should all be string.
According to the attribute type, which is set in the credential schema, values should be set to:
Text — text itself
Date — string with the number of seconds since epoch.
Number — number as string. If this number is float, than '.' used as decimal point "222.2222"
ImageURL -- url as string. // NOT USED YET
Enumeration -- numeric enumeration value as string, i.e. "0", "1",..etc
Actual value types will be casted on credential attribute display in the app according to the credential schema attribute types.