Maybe we can make this configurable later.
So users have the freedom to be more strict.
This commit partly reverts 62018f48c5.
Example to edit trust level:
```
gpg --edit-key somekeyid
gpg (GnuPG) 2.3.4; Copyright (C) 2021 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
pub rsa4096/keyid
created: 2020-06-26 expires: 2022-06-26 usage: SC
trust: unknown validity: full
sub rsa4096/keyid
created: 2020-06-26 expires: 2022-06-26 usage: E
[ full ] (1). xmpp:user@domain.de
gpg> trust
pub rsa4096/keyid
created: 2020-06-26 expires: 2022-06-26 usage: SC
trust: unknown validity: full
sub rsa4096/keyid
created: 2020-06-26 expires: 2022-06-26 usage: E
[ full ] (1). xmpp:user@domain.de
Please decide how far you trust this user to correctly verify other users' keys
(by looking at passports, checking fingerprints from different sources, etc.)
1 = I don't know or won't say
2 = I do NOT trust
3 = I trust marginally
4 = I trust fully
5 = I trust ultimately
m = back to the main menu
Your decision? 3
pub rsa4096/keyid
created: 2020-06-26 expires: 2022-06-26 usage: SC
trust: marginal validity: full
sub rsa4096/keyid
created: 2020-06-26 expires: 2022-06-26 usage: E
[ full ] (1). xmpp:user@domain.de
Please note that the shown key validity is not necessarily correct
unless you restart the program.
gpg> quit
```
* Added logging messages (INFO if key can not be used)
* Check owner_trust < GPGME_VALIDITY_MARGINAL
The key can not be used if the owner_trust is less than MARGINAL.
As all parts of the code invoking the `files_get_account_data_path()`
function did the same afterwards, a function has been added with the same
behavior.
1. create path
2. `mkdir` of that path
3. return final path
Signed-off-by: Steffen Jaeckel <jaeckel-floss@eyet-services.de>
Discovering Public Keys via PEP
* 4.3 Discovering Public Keys of a User
* 4.4 Requesting Public Keys
* Import Public Keys into GnuPG's local keyring.
Issue: #1331
src/pgp/gpg.c:p_ox_gpg_readkey
Used to read a public key from a file. The function will return the fingerprint
of the file and the base64 encoded key.
src/xmpp/ox.[hc]
ox_announce_public_key(const char* const filename) can be called from the /ox
announce <filename> command. The key within the file will be pushed on PEP and
the Metadata node will be set.
Issue: #1331
