Issue 443: Add observable:mutexName

[nsxtas]

This Pull Request resolves all requirements of Issue #443 .

changed submit to develop branch rather than master

Coordination

• [x] Pull Request is against correct branch
• [x] Pull Request is in, or reverted to, Draft status before Solutions Approval vote has passed. (N/A for bugfix)
• [x] CI passes in UCO feature branch
• [x] CI passes in UCO current unstable branch (07c6ad8)
• [x] CI passes in CASE current unstable branch tracking UCO's unstable as submodule (304ad29)
• [x] Impact on SHACL validation reviewed for CASE-Examples
• [x] Impact on SHACL validation remediated for CASE-Examples (N/A)
• [x] Impact on SHACL validation reviewed for casework.github.io
• [x] Impact on SHACL validation remediated for casework.github.io (N/A)
• [x] Milestone linked
• [x] Solutions Approval vote logged on corresponding Issue (N/A for bugfix)

[ajnelson-nist]

Converting PR to draft status until checklist review completed.

[ajnelson-nist]

@b0bkaT , once the CI in the unchecked checkboxes has passed, this is good to merge.