Include debug info when failing to load remote spec

[ulrikandersen]

Description

This PR aims to improve the debug experience when loading remote specification fails by:

1. Including part of remote spec content in error response from /remote endpoint. Makes it easier to debug why loading a remote spec fails.
2. Include remote spec name in the error message when decryption fails (Failed to decrypt remote specification auth for framna-docs-local (https://ws.fk.dk/dev/omdeler/api-docs). Perhaps a different public key was used?). Makes it easier to see which remote spec is failing.

Also the log level of 2. is changed to reflect that it is an expected error (e.g. wrong encryption key used).

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)