Move API Reference (#23777)

* merge mattermost-api-reference unchanged

* api: update repostiory paths

* api: drop GitPod for api (for now)

* api: improved node_modules target

* api: relocate GitHub actions to root

* Update .github/workflows/api.yml

Co-authored-by: Antonis Stamatiou <stamatiou.antonis@gmail.com>

* fix cache-dependency-path

* adopt node-version-file

* pin versions for uses

* tidy steps/runs

* api/.gitpod.yml: tidy

* api: rm now unused .gitlab-ci.yml

---------

Co-authored-by: Antonis Stamatiou <stamatiou.antonis@gmail.com>

api/v4/source/service_terms.yaml

@@ -0,0 +1,45 @@
+  /api/v4/terms_of_service:
+    get:
+      tags:
+        - terms of service
+      summary: Get latest terms of service
+      description: |
+        Get latest terms of service from the server
+
+        __Minimum server version__: 5.4
+        ##### Permissions
+        Must be authenticated.
+      operationId: GetTermsOfService
+      responses:
+        "200":
+          description: Terms of service fetched successfully
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/TermsOfService"
+        "400":
+          $ref: "#/components/responses/BadRequest"
+        "401":
+          $ref: "#/components/responses/Unauthorized"
+    post:
+      tags:
+        - terms of service
+      summary: Creates a new terms of service
+      description: |
+        Creates new terms of service
+
+        __Minimum server version__: 5.4
+        ##### Permissions
+        Must have `manage_system` permission.
+      operationId: CreateTermsOfService
+      responses:
+        "200":
+          description: terms of service fetched successfully
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/TermsOfService"
+        "400":
+          $ref: "#/components/responses/BadRequest"
+        "401":
+          $ref: "#/components/responses/Unauthorized"