Update use_cases.md

I added a paragraph here that clarifies that 'database administrators' are our primary type of user, before then elaborating on the capacities that HSDS offers to them. 

Can you check my framing there to make sure it reads correctly and seems apt?

docs/hsds/use_cases.md

@@ -13,6 +13,8 @@ Open Referral's agenda is set by the prerogatives of a set of four types of user
 
  Read more about each of these personas in [our Types of Use / User Personas documentation](https://docs.openreferral.org/en/latest/initiative/index.html?highlight=types%20of%20use#types-of-use-and-user-personas). 
 
+Practically speaking, *database administrators are the primary type of user* of HSDS and associated tools. It is still important to understand the needs of other types of users – as database administrators work to meet such needs – so we filter our understanding of end users' needs through the lense of data administrators' perspectives. 
+
 
 **Current Human Services Data Specification Capabilities**