Return failed status and code 400 for unsuccessful requests

[oliver-tarrant-tessella]

Acceptance criteria

Failed requests should return a status: fail and status code: 400 or 404, where appropriate, when unsuccessful requests are made. This includes:

• listpresent to a bucket that doesn't exist
• copydir, copynew, copyupdate when a directory doesn't exist or bucket doesn't exist
• deletefile when file doesn't exist or bucket doesn't exist
• createbucket when bucket name is rejected or already exists

[daniel-hunt-tessella]

Remember to add the relevant status and status code checks to the system tests when fixing these requests

[daniel-hunt-tessella]

Testing:

• listpresent for a bucket that does not exist returns a fail status and a 404 status code
• copydir, copynew, and copyupdate all return a 404 if the directory or bucket do not exist
• deletefile returns a 404 if the bucket or file does not exist
• createbucket returns a 400 if the bucket name is invalid or the bucket already exists