Add docs for creating an execution

docs/creating-an-execution.md

+---
+title: Creating an Execution
+has_children: false
+nav_order: 6
+---
+
+# Creating an Execution
+
+Theodolite Executions look similar to the following example.
+
+<!-- TODO align with upstream -->
+```yaml
+apiVersion: theodolite.com/v1
+kind: execution
+metadata:
+  name: theodolite-example-execution
+spec:
+  benchmark: "uc1-kstreams"
+  load:
+    loadType: "NumSensors"
+    loadValues: [25000, 50000]
+  resources:
+    resourceType: "Instances"
+    resourceValues: [1, 2]
+  slos:
+    - sloType: "lag trend"
+      prometheusUrl: "http://prometheus-operated:9090"
+      offset: 0
+      properties:
+        threshold: 2000
+        externalSloUrl: "http://localhost:80/evaluate-slope"
+        warmup: 60 # in seconds
+  execution:
+    strategy: "LinearSearch"
+    duration: 300 # in seconds
+    repetitions: 1
+    loadGenerationDelay: 30 # in seconds
+    restrictions:
+      - "LowerBound"
+  configOverrides:
+    - patcher:
+        type: "SchedulerNamePatcher"
+        resource: "uc1-kstreams-deployment.yaml"
+      value: "random-scheduler"
+```
+
+## Naming and Labeling
+
+Similar to [Kubernetes Jobs](https://kubernetes.io/docs/concepts/workloads/controllers/job/), Theodolite Executions are not automatically deleted after they are finished. Therefore, it is recommended to choose a meaningful name for your Execution. Additionally, you can add labels to your Executions as with any other Kubernetes resource.
+
+## Reference to a Benchmark
+
+An Execution always refers to a Benchmark. This benchmark has to be registered with Kubernetes once Theodolite starts an Execution. Otherwise, Theodolite aborts the Executions and marks it as *failed*.
+
+<!-- Benchmark state -->
+
+As a Benchmark may define multiple supported load and resource types, an Execution has to pick exactly one of each by its name. Additionally, it defines the set of load values and resource values the benchmark should be executed with.
+
+## Definition of SLOs
+
+SLOs provide a way to quantify whether a certain load intensity can be handled by a certain amount of provisioned resources.
+An Execution must at least specify one SLO to be checked.
+
+## Experimental Setup
+
+According to Theodolite's measurement method, isolated SLO experiments are performed for different combinations of load intensity and resource amounts.
+The experimental setup can be configured by:
+
+* A search strategy (`strategy`), which determines which load and resource combinations should be tested. Supported values are `FullSearch`, `LinearSearch` and `BinarySearch`. Additionally, a `restrictions` can be set to `LowerBound`.
+* The `duration` per SLO experiment in seconds.
+* The number of repetitions (`repetitions`) for each SLO experiment.
+* A `loadGenerationDelay`, specifying the time in seconds before the load generation starts.
+
+## Configuration Overrides
+
+In cases where only small modifications of a system under test should be benchmarked, it is not necessarily required to [create a new benchmark](creating-a-benchmark).
+Instead, also Executions allow to do small reconfigurations, such as switching on or off a specific Pod scheduler.
+
+This is done by defining `configOverrides` in the Execution. Each override consists of a patcher, defining which Kubernetes resource should be patched in which way, and a value the patcher is applied with.
+
+<!-- Further information: API Reference -->