Bug 1898509 - more details for SQL errors

The goal here is to track down some foreign key failures that we're
seeing, but don't have any context on where they're happening.

- Record a breadcrumb when we start to ingest different suggestion types.
- Record what we were doing when we saw an SQL error.  This should
  change the message from `FOREIGN KEY constraint failed` to something
  like `FOREIGN KEY constraint failed (context: mdn insert)`, which I
  think will help greatly.

I wanted to also record which field the foreign key error was happening
on, but AFAICT this is not possible with SQLite.

I added the `extend` crate to help with some of this code.  It's not
really needed, but I think it's worth the dependency. We've been using
it for `uniffi-bindgen-gecko-js` so it's already vetted.

DEPENDENCIES.md

@@ -12,6 +12,7 @@ the details of which are reproduced below.
 * [MIT License: bytes](#mit-license-bytes)
 * [MIT License: cargo_metadata](#mit-license-cargo_metadata)
 * [MIT License: caseless](#mit-license-caseless)
+* [MIT License: extend](#mit-license-extend)
 * [MIT License: generic-array](#mit-license-generic-array)
 * [MIT License: goblin](#mit-license-goblin)
 * [MIT License: h2](#mit-license-h2)
@@ -992,6 +993,34 @@ LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
+```
+-------------
+## MIT License: extend
+
+The following text applies to code linked from these dependencies:
+[extend](https://github.com/davidpdrsn/extend)
+
+```
+MIT License Copyright (c) 2020 David Pedersen
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is furnished
+to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice (including the next
+paragraph) shall be included in all copies or substantial portions of the
+Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS
+OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF
+OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
 ```
 -------------
 ## MIT License: generic-array

components/suggest/Cargo.toml

@@ -10,7 +10,9 @@ exclude = ["/android", "/ios"]
 [dependencies]
 anyhow = "1.0"
 chrono = "0.4"
+extend = "1.1"
 interrupt-support = { path = "../support/interrupt" }
+log = "0.4"
 once_cell = "1.5"
 parking_lot = ">=0.11,<=0.12"
 remote_settings = { path = "../remote_settings" }