fix: improve password validation flow (#15132)

Refers to #14984 

Currently, password validation is done backend side and is not explicit
enough so it can be painful to create first users.
We'd like to make this validation easier - but also duplicate it
frontend side to make it smoother.

Flows involved : 
- First user set password
- New user set password
- Change password

---------

Co-authored-by: BrunoQuaresma <bruno_nonato_quaresma@hotmail.com>

codersdk/users.go

@@ -178,6 +178,15 @@ type UpdateUserProfileRequest struct {
 	Name     string `json:"name" validate:"user_real_name"`
 }
 
+type ValidateUserPasswordRequest struct {
+	Password string `json:"password" validate:"required"`
+}
+
+type ValidateUserPasswordResponse struct {
+	Valid   bool   `json:"valid"`
+	Details string `json:"details"`
+}
+
 type UpdateUserAppearanceSettingsRequest struct {
 	ThemePreference string `json:"theme_preference" validate:"required"`
 }
@@ -407,6 +416,20 @@ func (c *Client) UpdateUserProfile(ctx context.Context, user string, req UpdateU
 	return resp, json.NewDecoder(res.Body).Decode(&resp)
 }
 
+// ValidateUserPassword validates the complexity of a user password and that it is secured enough.
+func (c *Client) ValidateUserPassword(ctx context.Context, req ValidateUserPasswordRequest) (ValidateUserPasswordResponse, error) {
+	res, err := c.Request(ctx, http.MethodPost, "/api/v2/users/validate-password", req)
+	if err != nil {
+		return ValidateUserPasswordResponse{}, err
+	}
+	defer res.Body.Close()
+	if res.StatusCode != http.StatusOK {
+		return ValidateUserPasswordResponse{}, ReadBodyAsError(res)
+	}
+	var resp ValidateUserPasswordResponse
+	return resp, json.NewDecoder(res.Body).Decode(&resp)
+}
+
 // UpdateUserStatus sets the user status to the given status
 func (c *Client) UpdateUserStatus(ctx context.Context, user string, status UserStatus) (User, error) {
 	path := fmt.Sprintf("/api/v2/users/%s/status/", user)