Implement NEP-413: signMessage method

[toteto]

Story

As a developer of application using the Near protocol, I want to use the NEP-413 proposal the methods it describes so I can sign piece of data for the purposes of authentication.

• NEP-413: NEP 0413: Add signMessage method to Wallet Standard NEPs#413

Acceptance Criteria

• The signMessage method is implemented according to the NEP-413 proposal.
• There is no gas fees nor transaction being made costing the user any Near.
• Mobile ok
• Tested

Unhappy Path

• Invalid parameters
• The user declines the signing of the message
• The account has no full-access key (Locked Account) and thus unable to perform the signing?

[gagdiez]

+1 on this Issue

[robdefeo]

+1 also

[SuperBatata]

is the signMessage method available or not yet ?