Refactor and add securities controller

lib/tradex_web/controllers/security_html/security_form.html.heex

@@ -0,0 +1,14 @@
+<.simple_form :let={f} for={@changeset} action={@action}>
+  <.error :if={@changeset.action}>
+    Oops, something went wrong! Please check the errors below.
+  </.error>
+  <.input field={f[:name]} type="text" label="Name" />
+  <.input field={f[:ticker]} type="text" label="Ticker" />
+  <.input field={f[:wkn]} type="text" label="Wkn" />
+  <.input field={f[:isin]} type="text" label="Isin" />
+  <.input field={f[:expiration_date]} type="date" label="Expiration date" />
+  <.input field={f[:strike_price]} type="number" label="Strike price" step="any" />
+  <:actions>
+    <.button>Save Security</.button>
+  </:actions>
+</.simple_form>