tests for link in email & subscription status

Cargo.lock

@@ -1459,6 +1459,15 @@ version = "0.5.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0717cef1bc8b636c6e1c1bbdefc09e6322da8a9321966e8928ef80d20f7f770f"
 
+[[package]]
+name = "linkify"
+version = "0.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f1dfa36d52c581e9ec783a7ce2a5e0143da6237be5811a0b3153fedfdbe9f780"
+dependencies = [
+ "memchr",
+]
+
 [[package]]
 name = "linux-raw-sys"
 version = "0.4.13"
@@ -3524,6 +3533,7 @@ dependencies = [
  "config",
  "fake",
  "lettre",
+ "linkify",
  "once_cell",
  "quickcheck",
  "quickcheck_macros",