As a software engineer
I want to create a new key/value date type with REST endpoints that support CRUD operations
So that data can easily be created and retrieved by providing a bucket name, an object name (which form the key) and content (for the data)

Given that PublicDataService and PnrService already exists to create data and to map names to addresses respectively
When adding key/value data
Then create a new KeyValueService
And then call create_public_data in PublicDataService  and remember the address
And then call PnrService to get/update or create a PNR record for it using the bucket name as PNR Zone 'name' and the object name as the PNR record key
And then return a KeyValue struct, which has 'bucket', 'object' and 'content' fields (as Strings)
And 'content' will hold base64 encoded text during transit to/from AntTP from the client (see ChunkService.create_chunk() for an example)

Given that PublicDataService and PnrService already exists to create data and to map names to addresses respectively
When retrieving key/value data
Then create a new KeyValueService
And then call PnrService to get a PNR record for it using the bucket name as PNR Zone 'name' and the object name as the PNR record key
And then call get_public_data in PublicDataService to retrieve the target data
And then return a KeyValue struct, which has 'bucket', 'object' and 'content' fields (as Strings), reflecting the input fields and the target data returned in the 'content'
And 'content' will hold base64 encoded text during transit to/from AntTP from the client (see ChunkService.create_chunk() for an example)

Given key_value_controller.rs will handle key/value REST requests
When adding key/value support
Then use pointer_controller.rs as an example
And define REST POST endpoint at /anttp-0/key_value to create data
And define REST GET endpoint at /anttp-0/key_value/{bucket}/{object} to retrieve data
And update /src/lib.rs with the new route

Given the postman collection has tests for REST endpoints
When adding KV support
Then the postman collection should be updated with the new /anttp-0/key_value POST endpoint
And /anttp-0/key_value/{bucket}/{object} GET endpoint
And newman should be used to validate

Implementation Notes

- Place any unit tests at the bottom of the same file as the associated production code
- Increment patch version of anttp package in Cargo.toml
- Create a copy of this issue description and save to /spec using the name of this issue as the filename (with lower underscore case, starting with the 5 char padded issue number, e.g. 00001_issue_title.txt)

Example KeyValue JSON:

```
{
  "bucket": "bucket_name",
  "object": "object_name",
  "content": "bXkgb2JqZWN0IGNvbnRlbnQ="
}
```