As a user i should not be able to delete a context in case it is attached to an existing pipeline

Currently a user can delete a context while it is still attached to a pipeline.
In such cases, the pipeline will not be runnable anymore.

We should not allow deleting contexts that are attached to existing pipelines.

We should support passing a 'force' flag that will go and clear all links to existing pipelines if a user wishes to delete the context forcely.