Constraint: AssetBed Relations

[gigincg]

Currently AssetBed Relations are ManyToMany. Even though the Relation should work the same, we need to enforce constraints for this.

• HL7Monitor Assets can have only 1 Bed Associated with it.
• ONVIFCamera Assets can have multiple beds associated with it. One Bed Can have multiple Assets too
• Assets that are neither HL7Monitor nor ONVIFCamera should not have Bed Relations

cc: @vigneshhari