feat: add 2.6 endpoints

[dated]

Summary

Adds the following API endpoints

GET

• bridgechains
• bridgechains/{id}
• businesses
• businesses/{id}
• businesses/{id}/bridgechains
• wallets/{id}/locks
• locks
• locks/{id}

POST

• businesses/search
• bridgechains/search
• locks/search
• locks/unlocked

Checklist

• Documentation (if necessary)
• Tests (if necessary)
• Ready to be merged

[dated]

The newly added, commented out tests require a general overhaul of the present fixtures and Models, which is out of scope for this PR.