refactor: merged sources of mail-headers,mail-internals,mail-core, mail

Originally it was palaned to do a merge with `--allow-unrelated-history`
but this can not be doesn as `mail-core` has a "invalid" history which
has a merge conflict **with itself**. So even rewinding the history on
a empty repo is not possible.

Instead the code was directly coppied over losing history.

But the history is still available in the different
`history-backup-*` branches. It is just that the past history
is decoupled from the current history.

110 files changed, 16915 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..a10770d
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,5 @@
+/target
+Cargo.lock
+.idea/
+.vscode/
+*.iml
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..79d33e8
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,7 @@
+[workspace]
+members = [
+    "mail",
+    "core",
+    "headers",
+    "internals"
+]
diff --git a/LICENSE-APACHE b/LICENSE-APACHE
new file mode 100644
index 0000000..56434b8
--- /dev/null
+++ b/LICENSE-APACHE
@@ -0,0 +1,201 @@
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