refactor/add-url

[bwalsh]

data-client $ tree indexd/
indexd/
├── add_url.go                                 // ! Add URL use case - not indexd. AddURL does not belong here, UpsertIndexdRecord does.
├── client.go                                  // Client implementation for indexd
├── client_test.go                             // Tests for client.go
├── convert.go                                 // Conversion utilities to/from indexd records
├── drs
│   ├── drs.go                                 // ! DRS related functionality  - not indexd
│   └── types.go                               // ! DRS related types - not indexd 
├── hash
│   ├── hash.go                                // Hashing utilities for indexd (& DRS?) 
│   └── hash_test.go
├── records.go                                 // Indexd record related functionality   
├── s3_utils.go                                // ! S3 utilities for add_url - not indexd
├── types.go                                   // Indexd related types   
└── types_test.go


# move the folllowing files out of indexd/ to their own packages in data_client
data-client
    ├── drs
    │   ├── drs.go                                 // DRS related functionality  - not indexd
    │   └── types.go                               // DRS related types - not indexd 
    ├── hash
    │   ├── hash.go                                // Hashing utilities for indexd (& DRS?) 
    │   └── hash_test.go
    ├── s3_utils.go                                // S3 utilities for add_url - not indexd


# move the following files out of indexd/ to their own package in git-drs
git-drs/cmd/add_url/
    ├── add_url.go                                 // ! Add URL use case - AddURL
    ├── tests
    │   ├── add-url-integration_test.go            // ! Add URL integration test - not indexd TODO 
    │   ├── client_read_test.go.todo               // TODO 
    │   ├── client_write_test.go.todo              // TODO
    │   └── mock_servers_test.go                   // Mock server tests for indexd TODO```