[User Story] Update an account in the service


**As a** user  
**I need** to update my account information  
**So that** my data stays current  

### Details and Assumptions
* PUT or PATCH to `/accounts/<id>`  
* Validate fields like name and address  

### Acceptance Criteria
```gherkin
Given updated valid data  
When a PUT request is sent  
Then the account should be updated