Update database semantic conventions

Release v0.6.0 of the opentelemetry spec included some changes to the
database semantic conventions, among them being changes to some of the
fields used to convert to Azure Dependency Targets etc.

open-telemetry/opentelemetry-specification#575

This commit updates the exporter to handle the new names for these
fields, however as the new equivalent to `db.instance` is `db.name`,
which can change when the database is changed inside a connection.

README.md

@@ -56,9 +56,9 @@ The following of the Span's attributes map to special fields in Application Insi
 | `db.statement`                           | Dependency Data                |
 | `http.host`                              | Dependency Target              |
 | `net.peer.name`                          | Dependency Target              |
-| `db.instance`                            | Dependency Target              |
+| `db.name`                                | Dependency Target              |
 | `http.status_code`                       | Dependency Result code         |
-| `db.type`                                | Dependency Type                |
+| `db.system`                              | Dependency Type                |
 | `messaging.system`                       | Dependency Type                |
 | `"HTTP"` if any `http.` attribute exists | Dependency Type                |
 | `"DB"` if any `db.` attribute exists     | Dependency Type                |

src/lib.rs

@@ -50,9 +50,9 @@
 //! | `db.statement`                           | Dependency Data                |
 //! | `http.host`                              | Dependency Target              |
 //! | `net.peer.name`                          | Dependency Target              |
-//! | `db.instance`                            | Dependency Target              |
+//! | `db.name`                                | Dependency Target              |
 //! | `http.status_code`                       | Dependency Result code         |
-//! | `db.type`                                | Dependency Type                |
+//! | `db.system`                              | Dependency Type                |
 //! | `messaging.system`                       | Dependency Type                |
 //! | `"HTTP"` if any `http.` attribute exists | Dependency Type                |
 //! | `"DB"` if any `db.` attribute exists     | Dependency Type                |
@@ -254,14 +254,14 @@ impl Exporter {
                     data.target = Some(String::from(*host));
                 } else if let Some(peer_name) = attrs.get("net.peer.name") {
                     data.target = Some(String::from(*peer_name));
-                } else if let Some(db_instance) = attrs.get("db.instance") {
-                    data.target = Some(String::from(*db_instance));
+                } else if let Some(db_name) = attrs.get("db.name") {
+                    data.target = Some(String::from(*db_name));
                 }
                 if span.span_kind == SpanKind::Internal {
                     data.type_ = Some("InProc".into());
                     data.success = Some(true);
-                } else if let Some(db_type) = attrs.get("db.type") {
-                    data.type_ = Some(String::from(*db_type));
+                } else if let Some(db_system) = attrs.get("db.system") {
+                    data.type_ = Some(String::from(*db_system));
                 } else if let Some(messaging_system) = attrs.get("messaging.system") {
                     data.type_ = Some(String::from(*messaging_system));
                 } else if attrs.keys().any(|x| x.starts_with("http.")) {