Sudomain support, register endpoint

[joepio]

• closes #502
• closes #288
• closes #489
• closes #556
• relates to #276
• relates to #544

TODO:

• [ ] Use new actix .full_uri() method instead of some hacky reconstruction. Will be added in 4.8 probably?
• [ ] Migrate trailing slash base URLs #895
• [ ] Run this on some new domain, check if everything works over there
• [x] Fix double path slash// in search results (and other places?)
• [x] Find all the format!( occurences where we combine things to create a URL, replace with URL::join.
• [ ] Find a strategy to deal with going to a subdomain and losing your local settings (specifically your key!)
• [ ] Consider invite-only registration
• [ ] Fix all_resources check for include_external. Currently does not properly use subdomains.
• [ ] Add E2E test for registration
• [ ] Remove the existing new drive behavior
• [x] Make sure users can't create resources on non-existing drives / subdomains. #556
• [x] E-mail registration + token support #276 #544
• [x] /resetPubkey type of endpoint, in case you lose your private key
• [ ] Fix changelog (currently incorrectly changes previous releases)
• [ ] Tenantized querie #570

PR Checklist:

• [x] Link to related issue
• [ ] Add changelog entry linking to issue
• [ ] Added tests (if needed)
• [ ] (If new feature) added in description / readme

[codesandbox[bot]]

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[codecov-commenter]

Codecov Report

Merging #505 (93ab91e) into master (f5af18d) will decrease coverage by 1.77%. Report is 2 commits behind head on master. The diff coverage is 56.35%.

:exclamation: Current head 93ab91e differs from pull request most recent head 7dac7b6. Consider uploading reports for the commit 7dac7b6 to get more accurate results

@@            Coverage Diff             @@
##           master     #505      +/-   ##
==========================================
- Coverage   66.12%   64.35%   -1.77%     
==========================================
  Files          73       79       +6     
  Lines        8200     8597     +397     
==========================================
+ Hits         5422     5533     +111     
- Misses       2778     3064     +286     

Files Changed	Coverage Δ
lib/src/authentication.rs	30.00% <0.00%> (ø)
lib/src/client.rs	21.97% <ø> (-7.88%)	:arrow_down:
lib/src/db/migrations.rs	23.68% <0.00%> (ø)
lib/src/db/query_index.rs	95.61% <ø> (ø)
lib/src/hierarchy.rs	59.03% <0.00%> (-22.64%)	:arrow_down:
lib/src/lib.rs	100.00% <ø> (ø)
lib/src/plugins/chatroom.rs	0.00% <ø> (ø)
lib/src/plugins/utils.rs	0.00% <0.00%> (ø)
lib/src/plugins/versioning.rs	71.11% <ø> (-0.63%)	:arrow_down:
server/src/commit_monitor.rs	22.07% <ø> (ø)
... and 35 more

... and 10 files with indirect coverage changes