Docs: Error handling guidelines

Is your feature request related to a problem? Please describe.
Need clear guidelines when to use error handling, and how to implement them.
There are several methods one could use.

• Nextflow error function.
• Groovy assert (assert <boolean> : <error_message_if_false).
• Groovy Exception (throw new Exception("Error message")).
• Nextflow log.error + system.exit(1).
• Nextflow exit <exitcode>, <message>

Describe the solution you'd like
Need docs describing when to include error handling, e.g. https://github.com/nf-core/modules/blob/e20e57f90b6787ac9a010a980cf6ea98bd990046/modules/lima/main.nf#L37 includes error handing for identically named input and output files.
https://github.com/nf-core/modules/blob/62da45b0e1202677a07e2da0ee9f6181466232fb/modules/deepvariant/main.nf#L7 for how to deal with no conda environment.

Modules:

• Let the tool handle the error message if it can.
• If it cannot, implement error handling with error.

Pipelines:

• Use error to report an error.

The Nextflow function error prints the message to both log and screen, and exits.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.

Start by reviewing the linked modules/lima/main.nf and modules/deepvariant/main.nf examples, along with the listed Nextflow and Groovy error-handling methods. Done means publishing documentation that explains when modules and pipelines should use each approach, including the stated tool-handling and error-function guidance.