update login requirement for mobile,

001_documentation/Requirements/REQ0016/index.md

@@ -2,7 +2,7 @@
 tags: cms, login-flow
 ---
 
-# login flow
+# CMS login flow
 
 ## description
 

001_documentation/Requirements/REQ0020/index.md

@@ -0,0 +1,37 @@
+---
+tags: mobile, login-flow
+---
+
+# Mobile login flow
+
+## description
+
+```mermaid
+graph TD;
+  Start-->A;
+  A-->B;
+  B-->C;
+  B-->D;
+  D-->E;
+  E-->F;
+  C-->G;
+  G-->A
+
+  F-->End;
+
+  A[greeting, asking username and password]
+  B[check if username and password is valid]
+  C[pasword failed]
+  D[pasword ok]
+  E[login success]
+  F[redirect to '/dashboard']
+
+  G[prompt user wrong username and password]
+
+  Start((start));
+  End((end))
+```
+
+### relations
+
+[REQ0016](../REQ0016/index.md)

001_documentation/Requirements/index.md

@@ -17,7 +17,8 @@
 - [REQ0013: cms dashboard](./REQ0013/index.md)
 - [REQ0014: mobile client](./REQ0014/index.md)
 - [REQ0015: pocketbase json schema to dbml converter](./REQ0015/index.md)
-- [REQ0016: login flow](./REQ0016/index.md)
+- [REQ0016: CMS login flow](./REQ0016/index.md)
 - [REQ0017: lesson page documentation](./REQ0017/index.md)
 - [REQ0018: family photo of frameworks](./REQ0018/index.md)
 - [REQ0019: System architecture](./REQ0019/index.md)
+- [REQ0020: Mobile login flow](./REQ0020/index.md)