Add deprecation note for Severity and Confidence levels

doc/api/vulnerability_findings.md

@@ -46,6 +46,9 @@ GET /projects/:id/vulnerability_findings?confidence=unknown,experimental
 GET /projects/:id/vulnerability_findings?pipeline_id=42
 ```
 
+CAUTION: **Deprecation:**
+Beginning with GitLab 12.9, the `undefined` severity level is deprecated and the `undefined` confidence level isn't reported for new vulnerabilities.
+
 | Attribute     | Type           | Required | Description                                                                                                                                                                         |
 | ------------- | -------------- | -------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
 | `id`          | integer/string | yes      | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) which the authenticated user is a member of.                                                        |

doc/user/application_security/container_scanning/index.md

@@ -347,6 +347,9 @@ it highlighted:
 }
 ```
 
+CAUTION: **Deprecation:**
+Beginning with GitLab 12.9, container scanning no longer reports `undefined` severity and confidence levels.
+
 Here is the description of the report file structure nodes and their meaning. All fields are mandatory to be present in
 the report JSON unless stated otherwise. Presence of optional fields depends on the underlying analyzers being used.
 

doc/user/application_security/dependency_scanning/index.md

@@ -355,6 +355,9 @@ it highlighted:
 }
 ```
 
+CAUTION: **Deprecation:**
+Beginning with GitLab 12.9, dependency scanning no longer reports `undefined` severity and confidence levels.
+
 Here is the description of the report file structure nodes and their meaning. All fields are mandatory to be present in
 the report JSON unless stated otherwise. Presence of optional fields depends on the underlying analyzers being used.
 

doc/user/application_security/sast/index.md

@@ -413,6 +413,9 @@ it highlighted:
 }
 ```
 
+CAUTION: **Deprecation:**
+Beginning with GitLab 12.9, SAST no longer reports `undefined` severity and confidence levels.
+
 Here is the description of the report file structure nodes and their meaning. All fields are mandatory in
 the report JSON unless stated otherwise. Presence of optional fields depends on the underlying analyzers being used.