### Describe Your Changes
Trimming content which is loaded from an external pass leads to obscure
issues in case user-defined input contained trimmed chars. For example.
user-defined password "foo\n" will become "foo" while user will expect
it to contain a new line.
---
For example, a user defines a password which ends with `\n`. This often
happens when user Kubernetes secrets and manually encodes value as
base64-encoded string.
In this case vmauth configuration might look like:
```
users:
- url_prefix:
- http://vminsert:8480/insert/0/prometheus/api/v1/write
name: foo
username: foo
password: "foobar\n"
```
vmagent configuration for this setup will use the following flags:
```
-remoteWrite.url=http://vmauth:8427/
-remoteWrite.basicAuth.passwordFile=/tmp/vmagent-password
-remoteWrite.basicAuth.username="foo"
```
Where `/tmp/vmagent-password` is a file with `foobar\n` password.
Before this change such configuration will result in `401 Unauthorized`
response received by vmagent since after file content will become
`foobar`.
---
An example with Kubernetes operator which uses a secret to reference the
same password in multiple configurations.
<details>
<summary>See full manifests</summary>
`Secret`:
```
apiVersion: v1
data:
name: Zm9v # foo
password: Zm9vYmFy # foobar\n
username: Zm9v= # foo
kind: Secret
metadata:
name: vmuser
```
`VMUser`:
```
apiVersion: operator.victoriametrics.com/v1beta1
kind: VMUser
metadata:
name: vmagents
spec:
generatePassword: false
name: vmagents
targetRefs:
- crd:
kind: VMAgent
name: some-other-agent
namespace: example
username: foo
# note - the secret above is referenced to provide password
passwordRef:
name: vmagent
key: password
```
`VMAgent`:
```
apiVersion: operator.victoriametrics.com/v1beta1
kind: VMAgent
metadata:
name: example
spec:
selectAllByDefault: true
scrapeInterval: 5s
replicaCount: 1
remoteWrite:
- url: "http://vmauth-vmauth-example:8427/api/v1/write"
# note - the secret above is referenced as well
basicAuth:
username:
name: vmagent
key: username
password:
name: vmagent
key: password
```
</details>
Since both config target exactly the same `Secret` object it is expected
to work, but apparently the result will be `401 Unauthrized` error.
### Checklist
The following checks are **mandatory**:
- [x] My change adheres [VictoriaMetrics contributing
guidelines](https://docs.victoriametrics.com/contributing/).
---------
Signed-off-by: Zakhar Bessarab <z.bessarab@victoriametrics.com>
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Co-authored-by: hagen1778 <roman@victoriametrics.com>
Examples:
1) -metricsAuthKey=file:///abs/path/to/file - reads flag value from the given absolute filepath
2) -metricsAuthKey=file://./relative/path/to/file - reads flag value from the given relative filepath
3) -metricsAuthKey=http://some-host/some/path?query_arg=abc - reads flag value from the given url
The flag value is automatically updated when the file contents changes.
