adjust the expected return code when user is missing "Tenant manager" admin rights

[reey]

Proposed changes

Improve the instructions about connecting to Cumulocity IoT:

• Use Forbidden and Unauthorized when referring to 403 and 401 error messages
• Include detailed description about each of the above errors
• Include a section of "common errors"
• Add info that SSO users are not supported

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Improvement (general improvements like code refactoring that doesn't explicitly fix a bug or add any new functionality)
• Documentation Update (if none of the other choices apply)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Paste Link to the issue

Checklist

• I have read the CONTRIBUTING doc
• I have signed the CLA (in all commits with git commit -s)
• I ran cargo fmt as mentioned in CODING_GUIDELINES
• I used cargo clippy as mentioned in CODING_GUIDELINES
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

Further comments

[reubenmiller]

Thanks, I was also in the middle of some other additional tips, so I will push a few commits of my own to this PR, e.g.

• notice that user/email is case sensitive
• add same tips to the additional cert upload page (same tips which are in the c8y getting started section)

[reubenmiller]

Thanks @reey for the PR. I just pushes a commit which expands on the common errors reasons and added a screenshot as well of the Cumulocity IoT Global Role which is required.

[reey]

@reubenmiller maybe also mention that SSO users are not supported?

[reubenmiller]

@reubenmiller maybe also mention that SSO users are not supported?

Do you know how a user can check if they are an SSO user or not?

[github-actions]

Robot Results

✅ Passed	❌ Failed	⏭️ Skipped	Total	Pass %	⏱️ Duration
373	0	3	373	100	45m55.936s