feat: add json-ld credential support

Description

Ticket #43 (closed)

This MR contains changes with new 3 endpoints

• Send json ld offer credential to another connection
• Sign any json-ld document and get signed version
• Get signed credential presentation (this presentation can be used in lated implementation for sending proof request with json-ld credential)

Related issues

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Testing

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Checklist

• I have updated the documentation (if necessary)
• I have added unit tests for new functionality (if applicable)
• My code follows the style guidelines of this project
• I have tested this code on my local machine before submitting this MR

Reviewers

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Additional Notes

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