50529: Content variables are too long

Allowed total length for message content variables is sum of key, value and JSON-specific characters' lengths.

Either too many variables are defined (max 100 in total), or too long keys (max 16 characters per variable), or too long values (max 256 characters per variable).

Follow the length limitations:

• variables: 100 in total;
• key: 16 characters per variable;
• value: 256 characters per variable.