(GH-538) Use TagList in ExtensionManifest

Prior to this change, the extension manifest struct defined the `tags`
field as `Option<Vec<String>>`. This change updates the field to use
the `TagList` newtype, which wraps `HashSet<Tag>` to provide better
semantics and JSON Schema for the type.

The `tags` field isn't directly accessed in any existing code.

Author: michaeltlombardi

lib/dsc-lib/src/extensions/extension_manifest.rs

@@ -11,7 +11,7 @@ use std::collections::HashMap;
 use crate::dscerror::DscError;
 use crate::extensions::{discover::DiscoverMethod, import::ImportMethod, secret::SecretMethod};
 use crate::schemas::dsc_repo::DscRepoSchema;
-use crate::types::FullyQualifiedTypeName;
+use crate::types::{FullyQualifiedTypeName, TagList};
 
 #[derive(Debug, Default, Clone, PartialEq, Deserialize, Serialize, JsonSchema, DscRepoSchema)]
 #[serde(deny_unknown_fields)]
@@ -41,7 +41,8 @@ pub struct ExtensionManifest {
     /// The description of the extension.
     pub description: Option<String>,
     /// Tags for the extension.
-    pub tags: Option<Vec<String>>,
+    #[serde(default)]
+    pub tags: TagList,
     /// Details how to call the Discover method of the extension.
     pub discover: Option<DiscoverMethod>,
     /// Details how to call the Import method of the extension.